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many places. The notable patch series are:
- nilfs2 folio conversion from Matthew Wilcox in "nilfs2: Folio
conversions for file paths".
- Additional nilfs2 folio conversion from Ryusuke Konishi in "nilfs2:
Folio conversions for directory paths".
- IA64 remnant removal in Heiko Carstens's "Remove unused code after
IA-64 removal".
- Arnd Bergmann has enabled the -Wmissing-prototypes warning everywhere
in "Treewide: enable -Wmissing-prototypes". This had some followup
fixes:
- Nathan Chancellor has cleaned up the hexagon build in the series
"hexagon: Fix up instances of -Wmissing-prototypes".
- Nathan also addressed some s390 warnings in "s390: A couple of
fixes for -Wmissing-prototypes".
- Arnd Bergmann addresses the same warnings for MIPS in his series
"mips: address -Wmissing-prototypes warnings".
- Baoquan He has made kexec_file operate in a top-down-fitting manner
similar to kexec_load in the series "kexec_file: Load kernel at top of
system RAM if required"
- Baoquan He has also added the self-explanatory "kexec_file: print out
debugging message if required".
- Some checkstack maintenance work from Tiezhu Yang in the series
"Modify some code about checkstack".
- Douglas Anderson has disentangled the watchdog code's logging when
multiple reports are occurring simultaneously. The series is "watchdog:
Better handling of concurrent lockups".
- Yuntao Wang has contributed some maintenance work on the crash code in
"crash: Some cleanups and fixes".
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Merge tag 'mm-nonmm-stable-2024-01-09-10-33' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull non-MM updates from Andrew Morton:
"Quite a lot of kexec work this time around. Many singleton patches in
many places. The notable patch series are:
- nilfs2 folio conversion from Matthew Wilcox in 'nilfs2: Folio
conversions for file paths'.
- Additional nilfs2 folio conversion from Ryusuke Konishi in 'nilfs2:
Folio conversions for directory paths'.
- IA64 remnant removal in Heiko Carstens's 'Remove unused code after
IA-64 removal'.
- Arnd Bergmann has enabled the -Wmissing-prototypes warning
everywhere in 'Treewide: enable -Wmissing-prototypes'. This had
some followup fixes:
- Nathan Chancellor has cleaned up the hexagon build in the series
'hexagon: Fix up instances of -Wmissing-prototypes'.
- Nathan also addressed some s390 warnings in 's390: A couple of
fixes for -Wmissing-prototypes'.
- Arnd Bergmann addresses the same warnings for MIPS in his series
'mips: address -Wmissing-prototypes warnings'.
- Baoquan He has made kexec_file operate in a top-down-fitting manner
similar to kexec_load in the series 'kexec_file: Load kernel at top
of system RAM if required'
- Baoquan He has also added the self-explanatory 'kexec_file: print
out debugging message if required'.
- Some checkstack maintenance work from Tiezhu Yang in the series
'Modify some code about checkstack'.
- Douglas Anderson has disentangled the watchdog code's logging when
multiple reports are occurring simultaneously. The series is
'watchdog: Better handling of concurrent lockups'.
- Yuntao Wang has contributed some maintenance work on the crash code
in 'crash: Some cleanups and fixes'"
* tag 'mm-nonmm-stable-2024-01-09-10-33' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (157 commits)
crash_core: fix and simplify the logic of crash_exclude_mem_range()
x86/crash: use SZ_1M macro instead of hardcoded value
x86/crash: remove the unused image parameter from prepare_elf_headers()
kdump: remove redundant DEFAULT_CRASH_KERNEL_LOW_SIZE
scripts/decode_stacktrace.sh: strip unexpected CR from lines
watchdog: if panicking and we dumped everything, don't re-enable dumping
watchdog/hardlockup: use printk_cpu_sync_get_irqsave() to serialize reporting
watchdog/softlockup: use printk_cpu_sync_get_irqsave() to serialize reporting
watchdog/hardlockup: adopt softlockup logic avoiding double-dumps
kexec_core: fix the assignment to kimage->control_page
x86/kexec: fix incorrect end address passed to kernel_ident_mapping_init()
lib/trace_readwrite.c:: replace asm-generic/io with linux/io
nilfs2: cpfile: fix some kernel-doc warnings
stacktrace: fix kernel-doc typo
scripts/checkstack.pl: fix no space expression between sp and offset
x86/kexec: fix incorrect argument passed to kexec_dprintk()
x86/kexec: use pr_err() instead of kexec_dprintk() when an error occurs
nilfs2: add missing set_freezable() for freezable kthread
kernel: relay: remove relay_file_splice_read dead code, doesn't work
docs: submit-checklist: remove all of "make namespacecheck"
...
When a CPU is taken offline, the contribution of its cfs_rqs to task_groups'
load may remain and will negatively impact the calculation of the share of
the online CPUs.
To fix this bug, clear the contribution of an offlining CPU to task groups'
load and skip its contribution while it is inactive.
Here's the reproducer of the anomaly, by Imran Khan:
"So far I have encountered only one rather lengthy way of reproducing this issue,
which is as follows:
1. Take a KVM guest (booted with 4 CPUs and can be scaled up to 124 CPUs) and
create 2 custom cgroups: /sys/fs/cgroup/cpu/test_group_1 and /sys/fs/cgroup/
cpu/test_group_2
2. Assign a CPU intensive workload to each of these cgroups and start the
workload.
For my tests I am using following app:
int main(int argc, char *argv[])
{
unsigned long count, i, val;
if (argc != 2) {
printf("usage: ./a.out <number of random nums to generate> \n");
return 0;
}
count = strtoul(argv[1], NULL, 10);
printf("Generating %lu random numbers \n", count);
for (i = 0; i < count; i++) {
val = rand();
val = val % 2;
//usleep(1);
}
printf("Generated %lu random numbers \n", count);
return 0;
}
Also since the system is booted with 4 CPUs, in order to completely load the
system I am also launching 4 instances of same test app under:
/sys/fs/cgroup/cpu/
3. We can see that both of the cgroups get similar CPU time:
# systemd-cgtop --depth 1
Path Tasks %CPU Memory Input/s Output/s
/ 659 - 5.5G - -
/system.slice - - 5.7G - -
/test_group_1 4 - - - -
/test_group_2 3 - - - -
/user.slice 31 - 56.5M - -
Path Tasks %CPU Memory Input/s Output/s
/ 659 394.6 5.5G - -
/test_group_2 3 65.7 - - -
/user.slice 29 55.1 48.0M - -
/test_group_1 4 47.3 - - -
/system.slice - 2.2 5.7G - -
Path Tasks %CPU Memory Input/s Output/s
/ 659 394.8 5.5G - -
/test_group_1 4 62.9 - - -
/user.slice 28 44.9 54.2M - -
/test_group_2 3 44.7 - - -
/system.slice - 0.9 5.7G - -
Path Tasks %CPU Memory Input/s Output/s
/ 659 394.4 5.5G - -
/test_group_2 3 58.8 - - -
/test_group_1 4 51.9 - - -
/user.slice 30 39.3 59.6M - -
/system.slice - 1.9 5.7G - -
Path Tasks %CPU Memory Input/s Output/s
/ 659 394.7 5.5G - -
/test_group_1 4 60.9 - - -
/test_group_2 3 57.9 - - -
/user.slice 28 43.5 36.9M - -
/system.slice - 3.0 5.7G - -
Path Tasks %CPU Memory Input/s Output/s
/ 659 395.0 5.5G - -
/test_group_1 4 66.8 - - -
/test_group_2 3 56.3 - - -
/user.slice 29 43.1 51.8M - -
/system.slice - 0.7 5.7G - -
4. Now move systemd-udevd to one of these test groups, say test_group_1, and
perform scale up to 124 CPUs followed by scale down back to 4 CPUs from the
host side.
5. Run the same workload i.e 4 instances of CPU hogger under /sys/fs/cgroup/cpu
and one instance of CPU hogger each in /sys/fs/cgroup/cpu/test_group_1 and
/sys/fs/cgroup/test_group_2.
It can be seen that test_group_1 (the one where systemd-udevd was moved) is getting
much less CPU time than the test_group_2, even though at this point of time both of
these groups have only CPU hogger running:
# systemd-cgtop --depth 1
Path Tasks %CPU Memory Input/s Output/s
/ 1219 - 5.4G - -
/system.slice - - 5.6G - -
/test_group_1 4 - - - -
/test_group_2 3 - - - -
/user.slice 26 - 91.3M - -
Path Tasks %CPU Memory Input/s Output/s
/ 1221 394.3 5.4G - -
/test_group_2 3 82.7 - - -
/test_group_1 4 14.3 - - -
/system.slice - 0.8 5.6G - -
/user.slice 26 0.4 91.2M - -
Path Tasks %CPU Memory Input/s Output/s
/ 1221 394.6 5.4G - -
/test_group_2 3 67.4 - - -
/system.slice - 24.6 5.6G - -
/test_group_1 4 12.5 - - -
/user.slice 26 0.4 91.2M - -
Path Tasks %CPU Memory Input/s Output/s
/ 1221 395.2 5.4G - -
/test_group_2 3 60.9 - - -
/system.slice - 27.9 5.6G - -
/test_group_1 4 12.2 - - -
/user.slice 26 0.4 91.2M - -
Path Tasks %CPU Memory Input/s Output/s
/ 1221 395.2 5.4G - -
/test_group_2 3 69.4 - - -
/test_group_1 4 13.9 - - -
/user.slice 28 1.6 92.0M - -
/system.slice - 1.0 5.6G - -
Path Tasks %CPU Memory Input/s Output/s
/ 1221 395.6 5.4G - -
/test_group_2 3 59.3 - - -
/test_group_1 4 14.1 - - -
/user.slice 28 1.3 92.2M - -
/system.slice - 0.7 5.6G - -
Path Tasks %CPU Memory Input/s Output/s
/ 1221 395.5 5.4G - -
/test_group_2 3 67.2 - - -
/test_group_1 4 11.5 - - -
/user.slice 28 1.3 92.5M - -
/system.slice - 0.6 5.6G - -
Path Tasks %CPU Memory Input/s Output/s
/ 1221 395.1 5.4G - -
/test_group_2 3 76.8 - - -
/test_group_1 4 12.9 - - -
/user.slice 28 1.3 92.8M - -
/system.slice - 1.2 5.6G - -
From sched_debug data it can be seen that in bad case the load.weight of per-CPU
sched entities corresponding to test_group_1 has reduced significantly and
also load_avg of test_group_1 remains much higher than that of test_group_2,
even though systemd-udevd stopped running long time back and at this point of
time both cgroups just have the CPU hogger app as running entity."
[ mingo: Added details from the original discussion, plus minor edits to the patch. ]
Reported-by: Imran Khan <imran.f.khan@oracle.com>
Tested-by: Imran Khan <imran.f.khan@oracle.com>
Tested-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Imran Khan <imran.f.khan@oracle.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Link: https://lore.kernel.org/r/20231223111545.62135-1-vincent.guittot@linaro.org
This variable became unused in:
5e963f2bd465 ("sched/fair: Commit to EEVDF")
Signed-off-by: Wang Jinchao <wangjinchao@xfusion.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/202312141319+0800-wangjinchao@xfusion.com
Running N CPU-bound tasks on an N CPUs platform:
- with asymmetric CPU capacity
- not being a DynamIq system (i.e. having a PKG level sched domain
without the SD_SHARE_PKG_RESOURCES flag set)
.. might result in a task placement where two tasks run on a big CPU
and none on a little CPU. This placement could be more optimal by
using all CPUs.
Testing platform:
Juno-r2:
- 2 big CPUs (1-2), maximum capacity of 1024
- 4 little CPUs (0,3-5), maximum capacity of 383
Testing workload ([1]):
Spawn 6 CPU-bound tasks. During the first 100ms (step 1), each tasks
is affine to a CPU, except for:
- one little CPU which is left idle.
- one big CPU which has 2 tasks affine.
After the 100ms (step 2), remove the cpumask affinity.
Behavior before the patch:
During step 2, the load balancer running from the idle CPU tags sched
domains as:
- little CPUs: 'group_has_spare'. Cf. group_has_capacity() and
group_is_overloaded(), 3 CPU-bound tasks run on a 4 CPUs
sched-domain, and the idle CPU provides enough spare capacity
regarding the imbalance_pct
- big CPUs: 'group_overloaded'. Indeed, 3 tasks run on a 2 CPUs
sched-domain, so the following path is used:
group_is_overloaded()
\-if (sgs->sum_nr_running <= sgs->group_weight) return true;
The following path which would change the migration type to
'migrate_task' is not taken:
calculate_imbalance()
\-if (env->idle != CPU_NOT_IDLE && env->imbalance == 0)
as the local group has some spare capacity, so the imbalance
is not 0.
The migration type requested is 'migrate_util' and the busiest
runqueue is the big CPU's runqueue having 2 tasks (each having a
utilization of 512). The idle little CPU cannot pull one of these
task as its capacity is too small for the task. The following path
is used:
detach_tasks()
\-case migrate_util:
\-if (util > env->imbalance) goto next;
After the patch:
As the number of failed balancing attempts grows (with
'nr_balance_failed'), progressively make it easier to migrate
a big task to the idling little CPU. A similar mechanism is
used for the 'migrate_load' migration type.
Improvement:
Running the testing workload [1] with the step 2 representing
a ~10s load for a big CPU:
Before patch: ~19.3s
After patch: ~18s (-6.7%)
Similar issue reported at:
https://lore.kernel.org/lkml/20230716014125.139577-1-qyousef@layalina.io/
Suggested-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Qais Yousef <qyousef@layalina.io>
Link: https://lore.kernel.org/r/20231206090043.634697-1-pierre.gondois@arm.com
With UTIL_EST_FASTUP now being permanent, we can take advantage of the
fact that the ewma jumps directly to a higher utilization at dequeue to
simplify util_est and remove the enqueued field.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Hongyan Xia <hongyan.xia2@arm.com>
Reviewed-by: Alex Shi <alexs@kernel.org>
Link: https://lore.kernel.org/r/20231201161652.1241695-3-vincent.guittot@linaro.org
sched_feat(UTIL_EST_FASTUP) has been added to easily disable the feature
in order to check for possibly related regressions. After 3 years, it has
never been used and no regression has been reported. Let's remove it
and make fast increase a permanent behavior.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Hongyan Xia <hongyan.xia2@arm.com>
Reviewed-by: Tang Yizhou <yizhou.tang@shopee.com>
Reviewed-by: Yanteng Si <siyanteng@loongson.cn> [for the Chinese translation]
Reviewed-by: Alex Shi <alexs@kernel.org>
Link: https://lore.kernel.org/r/20231201161652.1241695-2-vincent.guittot@linaro.org
These four functions have a normal definition for CONFIG_FAIR_GROUP_SCHED,
and empty one that is only referenced when FAIR_GROUP_SCHED is disabled
but CGROUP_SCHED is still enabled. If both are turned off, the functions
are still defined but the misisng prototype causes a W=1 warning:
kernel/sched/fair.c:12544:6: error: no previous prototype for 'free_fair_sched_group'
kernel/sched/fair.c:12546:5: error: no previous prototype for 'alloc_fair_sched_group'
kernel/sched/fair.c:12553:6: error: no previous prototype for 'online_fair_sched_group'
kernel/sched/fair.c:12555:6: error: no previous prototype for 'unregister_fair_sched_group'
Move the alternatives into the header as static inline functions with the
correct combination of #ifdef checks to avoid the warning without adding
even more complexity.
[A different patch with the same description got applied by accident
and was later reverted, but the original patch is still missing]
Link: https://lkml.kernel.org/r/20231123110506.707903-4-arnd@kernel.org
Fixes: 7aa55f2a5902 ("sched/fair: Move unused stub functions to header")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nicolas Schier <nicolas@fjasle.eu>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Rich Felker <dalias@libc.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Tudor Ambarus <tudor.ambarus@linaro.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Since reweight_entity() may have chance to change the weight of
cfs_rq->curr entity, we should also update_min_vruntime() if
this is the case
Fixes: eab03c23c2a1 ("sched/eevdf: Fix vruntime adjustment on reweight")
Signed-off-by: Yiwei Lin <s921975628@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Abel Wu <wuyun.abel@bytedance.com>
Link: https://lore.kernel.org/r/20231117080106.12890-1-s921975628@gmail.com
The current method to take into account uclamp hints when estimating the
target frequency can end in a situation where the selected target
frequency is finally higher than uclamp hints, whereas there are no real
needs. Such cases mainly happen because we are currently mixing the
traditional scheduler utilization signal with the uclamp performance
hints. By adding these 2 metrics, we loose an important information when
it comes to select the target frequency, and we have to make some
assumptions which can't fit all cases.
Rework the interface between the scheduler and schedutil governor in order
to propagate all information down to the cpufreq governor.
effective_cpu_util() interface changes and now returns the actual
utilization of the CPU with 2 optional inputs:
- The minimum performance for this CPU; typically the capacity to handle
the deadline task and the interrupt pressure. But also uclamp_min
request when available.
- The maximum targeting performance for this CPU which reflects the
maximum level that we would like to not exceed. By default it will be
the CPU capacity but can be reduced because of some performance hints
set with uclamp. The value can be lower than actual utilization and/or
min performance level.
A new sugov_effective_cpu_perf() interface is also available to compute
the final performance level that is targeted for the CPU, after applying
some cpufreq headroom and taking into account all inputs.
With these 2 functions, schedutil is now able to decide when it must go
above uclamp hints. It now also has a generic way to get the min
performance level.
The dependency between energy model and cpufreq governor and its headroom
policy doesn't exist anymore.
eenv_pd_max_util() asks schedutil for the targeted performance after
applying the impact of the waking task.
[ mingo: Refined the changelog & C comments. ]
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/20231122133904.446032-2-vincent.guittot@linaro.org
Lukasz Luba reported that a thread's util_est can significantly decrease as
a result of sharing the CPU with other threads.
The use case can be easily reproduced with a periodic task TA that runs 1ms
and sleeps 100us. When the task is alone on the CPU, its max utilization and
its util_est is around 888. If another similar task starts to run on the
same CPU, TA will have to share the CPU runtime and its maximum utilization
will decrease around half the CPU capacity (512) then TA's util_est will
follow this new maximum trend which is only the result of sharing the CPU
with others tasks.
Such situation can be detected with runnable_avg wich is close or
equal to util_avg when TA is alone, but increases above util_avg when TA
shares the CPU with other threads and wait on the runqueue.
[ We prefer an util_est that overestimate rather than under estimate
because in 1st case we will not provide enough performance to the
task which will remain under-provisioned, whereas in the other case we
will create some idle time which will enable to reduce contention and
as a result reduces the util_est so the overestimate will be transient
whereas the underestimate will remain. ]
[ mingo: Refined the changelog, added comments from the LKML discussion. ]
Reported-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/lkml/CAKfTPtDd-HhF-YiNTtL9i5k0PfJbF819Yxu4YquzfXgwi7voyw@mail.gmail.com/#t
Link: https://lore.kernel.org/r/20231122140119.472110-1-vincent.guittot@linaro.org
Cc: Hongyan Xia <hongyan.xia2@arm.com>
Low priority tasks (e.g., SCHED_OTHER) can suffer starvation if tasks
with higher priority (e.g., SCHED_FIFO) monopolize CPU(s).
RT Throttling has been introduced a while ago as a (mostly debug)
countermeasure one can utilize to reserve some CPU time for low priority
tasks (usually background type of work, e.g. workqueues, timers, etc.).
It however has its own problems (see documentation) and the undesired
effect of unconditionally throttling FIFO tasks even when no lower
priority activity needs to run (there are mechanisms to fix this issue
as well, but, again, with their own problems).
Introduce deadline servers to service low priority tasks needs under
starvation conditions. Deadline servers are built extending SCHED_DEADLINE
implementation to allow 2-level scheduling (a sched_deadline entity
becomes a container for lower priority scheduling entities).
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/4968601859d920335cf85822eb573a5f179f04b8.1699095159.git.bristot@kernel.org
Now that trace_sched_stat_runtime() no longer takes a vruntime
argument, the task specific bits are identical between
update_curr_common() and update_curr().
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tracing the runtime delta makes sense, observer can sum over time.
Tracing the absolute vruntime makes less sense, inconsistent:
absolute-vs-delta, but also vruntime delta can be computed from
runtime delta.
Removing the vruntime thing also makes the two tracepoint sites
identical, allowing to unify the code in a later patch.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
All classes use sched_entity::exec_start to track runtime and have
copies of the exact same code around to compute runtime.
Collapse all that.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/54d148a144f26d9559698c4dd82d8859038a7380.1699095159.git.bristot@kernel.org
Since the RB-tree is now sorted by deadline, let's first try the
leftmost entity which has the earliest virtual deadline. I've done
some benchmarks to see its effectiveness.
All the benchmarks are done inside a normal cpu cgroup in a clean
environment with cpu turbo disabled, on a dual-CPU Intel Xeon(R)
Platinum 8260 with 2 NUMA nodes each of which has 24C/48T.
hackbench: process/thread + pipe/socket + 1/2/4/8 groups
netperf: TCP/UDP + STREAM/RR + 24/48/72/96/192 threads
tbench: loopback 24/48/72/96/192 threads
schbench: 1/2/4/8 mthreads
direct: cfs_rq has only one entity
parity: RUN_TO_PARITY
fast: O(1) fastpath
slow: heap search
(%) direct parity fast slow
hackbench 92.95 2.02 4.91 0.12
netperf 68.08 6.60 24.18 1.14
tbench 67.55 11.22 20.61 0.62
schbench 69.91 2.65 25.73 1.71
The above results indicate that this fastpath really makes task
selection more efficient.
Signed-off-by: Abel Wu <wuyun.abel@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20231115033647.80785-4-wuyun.abel@bytedance.com
Sort the task timeline by virtual deadline and keep the min_vruntime
in the augmented tree, so we can avoid doubling the worst case cost
and make full use of the cached leftmost node to enable O(1) fastpath
picking in next patch.
Signed-off-by: Abel Wu <wuyun.abel@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20231115033647.80785-3-wuyun.abel@bytedance.com
Since commit fc137c0ddab2 ("sched/numa: enhance vma scanning logic")
NUMA Balancing allows updating PTEs to trap NUMA hinting faults if the
task had previously accessed VMA. However unconditional scan of VMAs are
allowed during initial phase of VMA creation until process's
mm numa_scan_seq reaches 2 even though current task had not accessed VMA.
Rationale:
- Without initial scan subsequent PTE update may never happen.
- Give fair opportunity to all the VMAs to be scanned and subsequently
understand the access pattern of all the VMAs.
But it has a corner case where, if a VMA is created after some time,
process's mm numa_scan_seq could be already greater than 2.
For e.g., values of mm numa_scan_seq when VMAs are created by running
mmtest autonuma benchmark briefly looks like:
start_seq=0 : 459
start_seq=2 : 138
start_seq=3 : 144
start_seq=4 : 8
start_seq=8 : 1
start_seq=9 : 1
This results in no unconditional PTE updates for those VMAs created after
some time.
Fix:
- Note down the initial value of mm numa_scan_seq in per VMA start_seq.
- Allow unconditional scan till start_seq + 2.
Result:
SUT: AMD EPYC Milan with 2 NUMA nodes 256 cpus.
base kernel: upstream 6.6-rc6 with Mels patches [1] applied.
kernbench
========== base patched %gain
Amean elsp-128 165.09 ( 0.00%) 164.78 * 0.19%*
Duration User 41404.28 41375.08
Duration System 9862.22 9768.48
Duration Elapsed 519.87 518.72
Ops NUMA PTE updates 1041416.00 831536.00
Ops NUMA hint faults 263296.00 220966.00
Ops NUMA pages migrated 258021.00 212769.00
Ops AutoNUMA cost 1328.67 1114.69
autonumabench
NUMA01_THREADLOCAL
==================
Amean elsp-NUMA01_THREADLOCAL 81.79 (0.00%) 67.74 * 17.18%*
Duration User 54832.73 47379.67
Duration System 75.00 185.75
Duration Elapsed 576.72 476.09
Ops NUMA PTE updates 394429.00 11121044.00
Ops NUMA hint faults 1001.00 8906404.00
Ops NUMA pages migrated 288.00 2998694.00
Ops AutoNUMA cost 7.77 44666.84
Signed-off-by: Raghavendra K T <raghavendra.kt@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Link: https://lore.kernel.org/r/2ea7cbce80ac7c62e90cbfb9653a7972f902439f.1697816692.git.raghavendra.kt@amd.com
should_we_balance is called for the decision to do load-balancing.
When sched ticks invoke this function, only one CPU should return
true. However, in the current code, two CPUs can return true. The
following situation, where b means busy and i means idle, is an
example, because CPU 0 and CPU 2 return true.
[0, 1] [2, 3]
b b i b
This fix checks if there exists an idle CPU with busy sibling(s)
after looking for a CPU on an idle core. If some idle CPUs with busy
siblings are found, just the first one should do load-balancing.
Fixes: b1bfeab9b002 ("sched/fair: Consider the idle state of the whole core for load balance")
Signed-off-by: Keisuke Nishimura <keisuke.nishimura@inria.fr>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Chen Yu <yu.c.chen@intel.com>
Reviewed-by: Shrikanth Hegde <sshegde@linux.vnet.ibm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20231031133821.1570861-1-keisuke.nishimura@inria.fr
vruntime of the (on_rq && !0-lag) entity needs to be adjusted when
it gets re-weighted, and the calculations can be simplified based
on the fact that re-weight won't change the w-average of all the
entities. Please check the proofs in comments.
But adjusting vruntime can also cause position change in RB-tree
hence require re-queue to fix up which might be costly. This might
be avoided by deferring adjustment to the time the entity actually
leaves tree (dequeue/pick), but that will negatively affect task
selection and probably not good enough either.
Fixes: 147f3efaa241 ("sched/fair: Implement an EEVDF-like scheduling policy")
Signed-off-by: Abel Wu <wuyun.abel@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20231107090510.71322-2-wuyun.abel@bytedance.com
included in this merge do the following:
- Kemeng Shi has contributed some compation maintenance work in the
series "Fixes and cleanups to compaction".
- Joel Fernandes has a patchset ("Optimize mremap during mutual
alignment within PMD") which fixes an obscure issue with mremap()'s
pagetable handling during a subsequent exec(), based upon an
implementation which Linus suggested.
- More DAMON/DAMOS maintenance and feature work from SeongJae Park i the
following patch series:
mm/damon: misc fixups for documents, comments and its tracepoint
mm/damon: add a tracepoint for damos apply target regions
mm/damon: provide pseudo-moving sum based access rate
mm/damon: implement DAMOS apply intervals
mm/damon/core-test: Fix memory leaks in core-test
mm/damon/sysfs-schemes: Do DAMOS tried regions update for only one apply interval
- In the series "Do not try to access unaccepted memory" Adrian Hunter
provides some fixups for the recently-added "unaccepted memory' feature.
To increase the feature's checking coverage. "Plug a few gaps where
RAM is exposed without checking if it is unaccepted memory".
- In the series "cleanups for lockless slab shrink" Qi Zheng has done
some maintenance work which is preparation for the lockless slab
shrinking code.
- Qi Zheng has redone the earlier (and reverted) attempt to make slab
shrinking lockless in the series "use refcount+RCU method to implement
lockless slab shrink".
- David Hildenbrand contributes some maintenance work for the rmap code
in the series "Anon rmap cleanups".
- Kefeng Wang does more folio conversions and some maintenance work in
the migration code. Series "mm: migrate: more folio conversion and
unification".
- Matthew Wilcox has fixed an issue in the buffer_head code which was
causing long stalls under some heavy memory/IO loads. Some cleanups
were added on the way. Series "Add and use bdev_getblk()".
- In the series "Use nth_page() in place of direct struct page
manipulation" Zi Yan has fixed a potential issue with the direct
manipulation of hugetlb page frames.
- In the series "mm: hugetlb: Skip initialization of gigantic tail
struct pages if freed by HVO" has improved our handling of gigantic
pages in the hugetlb vmmemmep optimizaton code. This provides
significant boot time improvements when significant amounts of gigantic
pages are in use.
- Matthew Wilcox has sent the series "Small hugetlb cleanups" - code
rationalization and folio conversions in the hugetlb code.
- Yin Fengwei has improved mlock()'s handling of large folios in the
series "support large folio for mlock"
- In the series "Expose swapcache stat for memcg v1" Liu Shixin has
added statistics for memcg v1 users which are available (and useful)
under memcg v2.
- Florent Revest has enhanced the MDWE (Memory-Deny-Write-Executable)
prctl so that userspace may direct the kernel to not automatically
propagate the denial to child processes. The series is named "MDWE
without inheritance".
- Kefeng Wang has provided the series "mm: convert numa balancing
functions to use a folio" which does what it says.
- In the series "mm/ksm: add fork-exec support for prctl" Stefan Roesch
makes is possible for a process to propagate KSM treatment across
exec().
- Huang Ying has enhanced memory tiering's calculation of memory
distances. This is used to permit the dax/kmem driver to use "high
bandwidth memory" in addition to Optane Data Center Persistent Memory
Modules (DCPMM). The series is named "memory tiering: calculate
abstract distance based on ACPI HMAT"
- In the series "Smart scanning mode for KSM" Stefan Roesch has
optimized KSM by teaching it to retain and use some historical
information from previous scans.
- Yosry Ahmed has fixed some inconsistencies in memcg statistics in the
series "mm: memcg: fix tracking of pending stats updates values".
- In the series "Implement IOCTL to get and optionally clear info about
PTEs" Peter Xu has added an ioctl to /proc/<pid>/pagemap which permits
us to atomically read-then-clear page softdirty state. This is mainly
used by CRIU.
- Hugh Dickins contributed the series "shmem,tmpfs: general maintenance"
- a bunch of relatively minor maintenance tweaks to this code.
- Matthew Wilcox has increased the use of the VMA lock over file-backed
page faults in the series "Handle more faults under the VMA lock". Some
rationalizations of the fault path became possible as a result.
- In the series "mm/rmap: convert page_move_anon_rmap() to
folio_move_anon_rmap()" David Hildenbrand has implemented some cleanups
and folio conversions.
- In the series "various improvements to the GUP interface" Lorenzo
Stoakes has simplified and improved the GUP interface with an eye to
providing groundwork for future improvements.
- Andrey Konovalov has sent along the series "kasan: assorted fixes and
improvements" which does those things.
- Some page allocator maintenance work from Kemeng Shi in the series
"Two minor cleanups to break_down_buddy_pages".
- In thes series "New selftest for mm" Breno Leitao has developed
another MM self test which tickles a race we had between madvise() and
page faults.
- In the series "Add folio_end_read" Matthew Wilcox provides cleanups
and an optimization to the core pagecache code.
- Nhat Pham has added memcg accounting for hugetlb memory in the series
"hugetlb memcg accounting".
- Cleanups and rationalizations to the pagemap code from Lorenzo
Stoakes, in the series "Abstract vma_merge() and split_vma()".
- Audra Mitchell has fixed issues in the procfs page_owner code's new
timestamping feature which was causing some misbehaviours. In the
series "Fix page_owner's use of free timestamps".
- Lorenzo Stoakes has fixed the handling of new mappings of sealed files
in the series "permit write-sealed memfd read-only shared mappings".
- Mike Kravetz has optimized the hugetlb vmemmap optimization in the
series "Batch hugetlb vmemmap modification operations".
- Some buffer_head folio conversions and cleanups from Matthew Wilcox in
the series "Finish the create_empty_buffers() transition".
- As a page allocator performance optimization Huang Ying has added
automatic tuning to the allocator's per-cpu-pages feature, in the series
"mm: PCP high auto-tuning".
- Roman Gushchin has contributed the patchset "mm: improve performance
of accounted kernel memory allocations" which improves their performance
by ~30% as measured by a micro-benchmark.
- folio conversions from Kefeng Wang in the series "mm: convert page
cpupid functions to folios".
- Some kmemleak fixups in Liu Shixin's series "Some bugfix about
kmemleak".
- Qi Zheng has improved our handling of memoryless nodes by keeping them
off the allocation fallback list. This is done in the series "handle
memoryless nodes more appropriately".
- khugepaged conversions from Vishal Moola in the series "Some
khugepaged folio conversions".
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Merge tag 'mm-stable-2023-11-01-14-33' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull MM updates from Andrew Morton:
"Many singleton patches against the MM code. The patch series which are
included in this merge do the following:
- Kemeng Shi has contributed some compation maintenance work in the
series 'Fixes and cleanups to compaction'
- Joel Fernandes has a patchset ('Optimize mremap during mutual
alignment within PMD') which fixes an obscure issue with mremap()'s
pagetable handling during a subsequent exec(), based upon an
implementation which Linus suggested
- More DAMON/DAMOS maintenance and feature work from SeongJae Park i
the following patch series:
mm/damon: misc fixups for documents, comments and its tracepoint
mm/damon: add a tracepoint for damos apply target regions
mm/damon: provide pseudo-moving sum based access rate
mm/damon: implement DAMOS apply intervals
mm/damon/core-test: Fix memory leaks in core-test
mm/damon/sysfs-schemes: Do DAMOS tried regions update for only one apply interval
- In the series 'Do not try to access unaccepted memory' Adrian
Hunter provides some fixups for the recently-added 'unaccepted
memory' feature. To increase the feature's checking coverage. 'Plug
a few gaps where RAM is exposed without checking if it is
unaccepted memory'
- In the series 'cleanups for lockless slab shrink' Qi Zheng has done
some maintenance work which is preparation for the lockless slab
shrinking code
- Qi Zheng has redone the earlier (and reverted) attempt to make slab
shrinking lockless in the series 'use refcount+RCU method to
implement lockless slab shrink'
- David Hildenbrand contributes some maintenance work for the rmap
code in the series 'Anon rmap cleanups'
- Kefeng Wang does more folio conversions and some maintenance work
in the migration code. Series 'mm: migrate: more folio conversion
and unification'
- Matthew Wilcox has fixed an issue in the buffer_head code which was
causing long stalls under some heavy memory/IO loads. Some cleanups
were added on the way. Series 'Add and use bdev_getblk()'
- In the series 'Use nth_page() in place of direct struct page
manipulation' Zi Yan has fixed a potential issue with the direct
manipulation of hugetlb page frames
- In the series 'mm: hugetlb: Skip initialization of gigantic tail
struct pages if freed by HVO' has improved our handling of gigantic
pages in the hugetlb vmmemmep optimizaton code. This provides
significant boot time improvements when significant amounts of
gigantic pages are in use
- Matthew Wilcox has sent the series 'Small hugetlb cleanups' - code
rationalization and folio conversions in the hugetlb code
- Yin Fengwei has improved mlock()'s handling of large folios in the
series 'support large folio for mlock'
- In the series 'Expose swapcache stat for memcg v1' Liu Shixin has
added statistics for memcg v1 users which are available (and
useful) under memcg v2
- Florent Revest has enhanced the MDWE (Memory-Deny-Write-Executable)
prctl so that userspace may direct the kernel to not automatically
propagate the denial to child processes. The series is named 'MDWE
without inheritance'
- Kefeng Wang has provided the series 'mm: convert numa balancing
functions to use a folio' which does what it says
- In the series 'mm/ksm: add fork-exec support for prctl' Stefan
Roesch makes is possible for a process to propagate KSM treatment
across exec()
- Huang Ying has enhanced memory tiering's calculation of memory
distances. This is used to permit the dax/kmem driver to use 'high
bandwidth memory' in addition to Optane Data Center Persistent
Memory Modules (DCPMM). The series is named 'memory tiering:
calculate abstract distance based on ACPI HMAT'
- In the series 'Smart scanning mode for KSM' Stefan Roesch has
optimized KSM by teaching it to retain and use some historical
information from previous scans
- Yosry Ahmed has fixed some inconsistencies in memcg statistics in
the series 'mm: memcg: fix tracking of pending stats updates
values'
- In the series 'Implement IOCTL to get and optionally clear info
about PTEs' Peter Xu has added an ioctl to /proc/<pid>/pagemap
which permits us to atomically read-then-clear page softdirty
state. This is mainly used by CRIU
- Hugh Dickins contributed the series 'shmem,tmpfs: general
maintenance', a bunch of relatively minor maintenance tweaks to
this code
- Matthew Wilcox has increased the use of the VMA lock over
file-backed page faults in the series 'Handle more faults under the
VMA lock'. Some rationalizations of the fault path became possible
as a result
- In the series 'mm/rmap: convert page_move_anon_rmap() to
folio_move_anon_rmap()' David Hildenbrand has implemented some
cleanups and folio conversions
- In the series 'various improvements to the GUP interface' Lorenzo
Stoakes has simplified and improved the GUP interface with an eye
to providing groundwork for future improvements
- Andrey Konovalov has sent along the series 'kasan: assorted fixes
and improvements' which does those things
- Some page allocator maintenance work from Kemeng Shi in the series
'Two minor cleanups to break_down_buddy_pages'
- In thes series 'New selftest for mm' Breno Leitao has developed
another MM self test which tickles a race we had between madvise()
and page faults
- In the series 'Add folio_end_read' Matthew Wilcox provides cleanups
and an optimization to the core pagecache code
- Nhat Pham has added memcg accounting for hugetlb memory in the
series 'hugetlb memcg accounting'
- Cleanups and rationalizations to the pagemap code from Lorenzo
Stoakes, in the series 'Abstract vma_merge() and split_vma()'
- Audra Mitchell has fixed issues in the procfs page_owner code's new
timestamping feature which was causing some misbehaviours. In the
series 'Fix page_owner's use of free timestamps'
- Lorenzo Stoakes has fixed the handling of new mappings of sealed
files in the series 'permit write-sealed memfd read-only shared
mappings'
- Mike Kravetz has optimized the hugetlb vmemmap optimization in the
series 'Batch hugetlb vmemmap modification operations'
- Some buffer_head folio conversions and cleanups from Matthew Wilcox
in the series 'Finish the create_empty_buffers() transition'
- As a page allocator performance optimization Huang Ying has added
automatic tuning to the allocator's per-cpu-pages feature, in the
series 'mm: PCP high auto-tuning'
- Roman Gushchin has contributed the patchset 'mm: improve
performance of accounted kernel memory allocations' which improves
their performance by ~30% as measured by a micro-benchmark
- folio conversions from Kefeng Wang in the series 'mm: convert page
cpupid functions to folios'
- Some kmemleak fixups in Liu Shixin's series 'Some bugfix about
kmemleak'
- Qi Zheng has improved our handling of memoryless nodes by keeping
them off the allocation fallback list. This is done in the series
'handle memoryless nodes more appropriately'
- khugepaged conversions from Vishal Moola in the series 'Some
khugepaged folio conversions'"
[ bcachefs conflicts with the dynamically allocated shrinkers have been
resolved as per Stephen Rothwell in
https://lore.kernel.org/all/20230913093553.4290421e@canb.auug.org.au/
with help from Qi Zheng.
The clone3 test filtering conflict was half-arsed by yours truly ]
* tag 'mm-stable-2023-11-01-14-33' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (406 commits)
mm/damon/sysfs: update monitoring target regions for online input commit
mm/damon/sysfs: remove requested targets when online-commit inputs
selftests: add a sanity check for zswap
Documentation: maple_tree: fix word spelling error
mm/vmalloc: fix the unchecked dereference warning in vread_iter()
zswap: export compression failure stats
Documentation: ubsan: drop "the" from article title
mempolicy: migration attempt to match interleave nodes
mempolicy: mmap_lock is not needed while migrating folios
mempolicy: alloc_pages_mpol() for NUMA policy without vma
mm: add page_rmappable_folio() wrapper
mempolicy: remove confusing MPOL_MF_LAZY dead code
mempolicy: mpol_shared_policy_init() without pseudo-vma
mempolicy trivia: use pgoff_t in shared mempolicy tree
mempolicy trivia: slightly more consistent naming
mempolicy trivia: delete those ancient pr_debug()s
mempolicy: fix migrate_pages(2) syscall return nr_failed
kernfs: drop shared NUMA mempolicy hooks
hugetlbfs: drop shared NUMA mempolicy pretence
mm/damon/sysfs-test: add a unit test for damon_sysfs_set_targets()
...
Convert to use folio_xchg_last_cpupid() in should_numa_migrate_memory().
Link: https://lkml.kernel.org/r/20231018140806.2783514-14-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Convert to use folio_xchg_access_time() in numa_hint_fault_latency().
Link: https://lkml.kernel.org/r/20231018140806.2783514-9-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Chen Yu reports a hackbench regression of cluster wakeup when
hackbench threads equal to the CPU number [1]. Analysis shows
it's because we wake up more on the target CPU even if the
prev_cpu is a good wakeup candidate and leads to the decrease
of the CPU utilization.
Generally if the task's prev_cpu is idle we'll wake up the task
on it without scanning. On cluster machines we'll try to wake up
the task in the same cluster of the target for better cache
affinity, so if the prev_cpu is idle but not sharing the same
cluster with the target we'll still try to find an idle CPU within
the cluster. This will improve the performance at low loads on
cluster machines. But in the issue above, if the prev_cpu is idle
but not in the cluster with the target CPU, we'll try to scan an
idle one in the cluster. But since the system is busy, we're
likely to fail the scanning and use target instead, even if
the prev_cpu is idle. Then leads to the regression.
This patch solves this in 2 steps:
o record the prev_cpu/recent_used_cpu if they're good wakeup
candidates but not sharing the cluster with the target.
o on scanning failure use the prev_cpu/recent_used_cpu if
they're recorded as idle
[1] https://lore.kernel.org/all/ZGzDLuVaHR1PAYDt@chenyu5-mobl1/
Closes: https://lore.kernel.org/all/ZGsLy83wPIpamy6x@chenyu5-mobl1/
Reported-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Tested-and-reviewed-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20231019033323.54147-4-yangyicong@huawei.com
For platforms having clusters like Kunpeng920, CPUs within the same cluster
have lower latency when synchronizing and accessing shared resources like
cache. Thus, this patch tries to find an idle cpu within the cluster of the
target CPU before scanning the whole LLC to gain lower latency. This
will be implemented in 2 steps in select_idle_sibling():
1. When the prev_cpu/recent_used_cpu are good wakeup candidates, use them
if they're sharing cluster with the target CPU. Otherwise trying to
scan for an idle CPU in the target's cluster.
2. Scanning the cluster prior to the LLC of the target CPU for an
idle CPU to wakeup.
Testing has been done on Kunpeng920 by pinning tasks to one numa and two
numa. On Kunpeng920, Each numa has 8 clusters and each cluster has 4 CPUs.
With this patch, We noticed enhancement on tbench and netperf within one
numa or cross two numa on top of tip-sched-core commit
9b46f1abc6d4 ("sched/debug: Print 'tgid' in sched_show_task()")
tbench results (node 0):
baseline patched
1: 327.2833 372.4623 ( 13.80%)
4: 1320.5933 1479.8833 ( 12.06%)
8: 2638.4867 2921.5267 ( 10.73%)
16: 5282.7133 5891.5633 ( 11.53%)
32: 9810.6733 9877.3400 ( 0.68%)
64: 7408.9367 7447.9900 ( 0.53%)
128: 6203.2600 6191.6500 ( -0.19%)
tbench results (node 0-1):
baseline patched
1: 332.0433 372.7223 ( 12.25%)
4: 1325.4667 1477.6733 ( 11.48%)
8: 2622.9433 2897.9967 ( 10.49%)
16: 5218.6100 5878.2967 ( 12.64%)
32: 10211.7000 11494.4000 ( 12.56%)
64: 13313.7333 16740.0333 ( 25.74%)
128: 13959.1000 14533.9000 ( 4.12%)
netperf results TCP_RR (node 0):
baseline patched
1: 76546.5033 90649.9867 ( 18.42%)
4: 77292.4450 90932.7175 ( 17.65%)
8: 77367.7254 90882.3467 ( 17.47%)
16: 78519.9048 90938.8344 ( 15.82%)
32: 72169.5035 72851.6730 ( 0.95%)
64: 25911.2457 25882.2315 ( -0.11%)
128: 10752.6572 10768.6038 ( 0.15%)
netperf results TCP_RR (node 0-1):
baseline patched
1: 76857.6667 90892.2767 ( 18.26%)
4: 78236.6475 90767.3017 ( 16.02%)
8: 77929.6096 90684.1633 ( 16.37%)
16: 77438.5873 90502.5787 ( 16.87%)
32: 74205.6635 88301.5612 ( 19.00%)
64: 69827.8535 71787.6706 ( 2.81%)
128: 25281.4366 25771.3023 ( 1.94%)
netperf results UDP_RR (node 0):
baseline patched
1: 96869.8400 110800.8467 ( 14.38%)
4: 97744.9750 109680.5425 ( 12.21%)
8: 98783.9863 110409.9637 ( 11.77%)
16: 99575.0235 110636.2435 ( 11.11%)
32: 95044.7250 97622.8887 ( 2.71%)
64: 32925.2146 32644.4991 ( -0.85%)
128: 12859.2343 12824.0051 ( -0.27%)
netperf results UDP_RR (node 0-1):
baseline patched
1: 97202.4733 110190.1200 ( 13.36%)
4: 95954.0558 106245.7258 ( 10.73%)
8: 96277.1958 105206.5304 ( 9.27%)
16: 97692.7810 107927.2125 ( 10.48%)
32: 79999.6702 103550.2999 ( 29.44%)
64: 80592.7413 87284.0856 ( 8.30%)
128: 27701.5770 29914.5820 ( 7.99%)
Note neither Kunpeng920 nor x86 Jacobsville supports SMT, so the SMT branch
in the code has not been tested but it supposed to work.
Chen Yu also noticed this will improve the performance of tbench and
netperf on a 24 CPUs Jacobsville machine, there are 4 CPUs in one
cluster sharing L2 Cache.
[https://lore.kernel.org/lkml/Ytfjs+m1kUs0ScSn@worktop.programming.kicks-ass.net]
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
Reviewed-by: Chen Yu <yu.c.chen@intel.com>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Tested-and-reviewed-by: Chen Yu <yu.c.chen@intel.com>
Tested-by: Yicong Yang <yangyicong@hisilicon.com>
Link: https://lkml.kernel.org/r/20231019033323.54147-3-yangyicong@huawei.com
The 'curr' argument of pick_next_entity() has become unused after
the EEVDF changes.
[ mingo: Updated the changelog. ]
Signed-off-by: Yiwei Lin <s921975628@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231020055617.42064-1-s921975628@gmail.com
How ILB is triggered without IPIs is cryptic. Out of mercy for future
code readers, document it in code comments.
The comments are derived from a discussion with Vincent in a past
review.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231020014031.919742-2-joel@joelfernandes.org
The cpupid (or access time) is stored in the head page for THP, so it is
safely to make should_numa_migrate_memory() and numa_hint_fault_latency()
to take a folio. This is in preparation for large folio numa balancing.
Link: https://lkml.kernel.org/r/20230921074417.24004-7-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Kuyo reported sporadic failures on a sched_setaffinity() vs CPU
hotplug stress-test -- notably affine_move_task() remains stuck in
wait_for_completion(), leading to a hung-task detector warning.
Specifically, it was reported that stop_one_cpu_nowait(.fn =
migration_cpu_stop) returns false -- this stopper is responsible for
the matching complete().
The race scenario is:
CPU0 CPU1
// doing _cpu_down()
__set_cpus_allowed_ptr()
task_rq_lock();
takedown_cpu()
stop_machine_cpuslocked(take_cpu_down..)
<PREEMPT: cpu_stopper_thread()
MULTI_STOP_PREPARE
...
__set_cpus_allowed_ptr_locked()
affine_move_task()
task_rq_unlock();
<PREEMPT: cpu_stopper_thread()\>
ack_state()
MULTI_STOP_RUN
take_cpu_down()
__cpu_disable();
stop_machine_park();
stopper->enabled = false;
/>
/>
stop_one_cpu_nowait(.fn = migration_cpu_stop);
if (stopper->enabled) // false!!!
That is, by doing stop_one_cpu_nowait() after dropping rq-lock, the
stopper thread gets a chance to preempt and allows the cpu-down for
the target CPU to complete.
OTOH, since stop_one_cpu_nowait() / cpu_stop_queue_work() needs to
issue a wakeup, it must not be ran under the scheduler locks.
Solve this apparent contradiction by keeping preemption disabled over
the unlock + queue_stopper combination:
preempt_disable();
task_rq_unlock(...);
if (!stop_pending)
stop_one_cpu_nowait(...)
preempt_enable();
This respects the lock ordering contraints while still avoiding the
above race. That is, if we find the CPU is online under rq-lock, the
targeted stop_one_cpu_nowait() must succeed.
Apply this pattern to all similar stop_one_cpu_nowait() invocations.
Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Reported-by: "Kuyo Chang (張建文)" <Kuyo.Chang@mediatek.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: "Kuyo Chang (張建文)" <Kuyo.Chang@mediatek.com>
Link: https://lkml.kernel.org/r/20231010200442.GA16515@noisy.programming.kicks-ass.net
While reworking the x86 topology code Thomas tripped over creating a 'DIE' domain
for the package mask. :-)
Since these names are CONFIG_SCHED_DEBUG=y only, rename them to make the
name less ambiguous.
[ Shrikanth Hegde: rename on s390 as well. ]
[ Valentin Schneider: also rename it in the comments. ]
[ mingo: port to recent kernels & find all remaining occurances. ]
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Valentin Schneider <vschneid@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Acked-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20230712141056.GI3100107@hirez.programming.kicks-ass.net
VMAs are skipped if there is no recent fault activity but this represents
a chicken-and-egg problem as there may be no fault activity if the PTEs
are never updated to trap NUMA hints. There is an indirect reliance on
scanning to be forced early in the lifetime of a task but this may fail
to detect changes in phase behaviour. Force inactive VMAs to be scanned
when all other eligible VMAs have been updated within the same scan
sequence.
Test results in general look good with some changes in performance, both
negative and positive, depending on whether the additional scanning and
faulting was beneficial or not to the workload. The autonuma benchmark
workload NUMA01_THREADLOCAL was picked for closer examination. The workload
creates two processes with numerous threads and thread-local storage that
is zero-filled in a loop. It exercises the corner case where unrelated
threads may skip VMAs that are thread-local to another thread and still
has some VMAs that inactive while the workload executes.
The VMA skipping activity frequency with and without the patch:
6.6.0-rc2-sched-numabtrace-v1
=============================
649 reason=scan_delay
9,094 reason=unsuitable
48,915 reason=shared_ro
143,919 reason=inaccessible
193,050 reason=pid_inactive
6.6.0-rc2-sched-numabselective-v1
=============================
146 reason=seq_completed
622 reason=ignore_pid_inactive
624 reason=scan_delay
6,570 reason=unsuitable
16,101 reason=shared_ro
27,608 reason=inaccessible
41,939 reason=pid_inactive
Note that with the patch applied, the PID activity is ignored
(ignore_pid_inactive) to ensure a VMA with some activity is completely
scanned. In addition, a small number of VMAs are scanned when no other
eligible VMA is available during a single scan window (seq_completed).
The number of times a VMA is skipped due to no PID activity from the
scanning task (pid_inactive) drops dramatically. It is expected that
this will increase the number of PTEs updated for NUMA hinting faults
as well as hinting faults but these represent PTEs that would otherwise
have been missed. The tradeoff is scan+fault overhead versus improving
locality due to migration.
On a 2-socket Cascade Lake test machine, the time to complete the
workload is as follows;
6.6.0-rc2 6.6.0-rc2
sched-numabtrace-v1 sched-numabselective-v1
Min elsp-NUMA01_THREADLOCAL 174.22 ( 0.00%) 117.64 ( 32.48%)
Amean elsp-NUMA01_THREADLOCAL 175.68 ( 0.00%) 123.34 * 29.79%*
Stddev elsp-NUMA01_THREADLOCAL 1.20 ( 0.00%) 4.06 (-238.20%)
CoeffVar elsp-NUMA01_THREADLOCAL 0.68 ( 0.00%) 3.29 (-381.70%)
Max elsp-NUMA01_THREADLOCAL 177.18 ( 0.00%) 128.03 ( 27.74%)
The time to complete the workload is reduced by almost 30%:
6.6.0-rc2 6.6.0-rc2
sched-numabtrace-v1 sched-numabselective-v1 /
Duration User 91201.80 63506.64
Duration System 2015.53 1819.78
Duration Elapsed 1234.77 868.37
In this specific case, system CPU time was not increased but it's not
universally true.
From vmstat, the NUMA scanning and fault activity is as follows;
6.6.0-rc2 6.6.0-rc2
sched-numabtrace-v1 sched-numabselective-v1
Ops NUMA base-page range updates 64272.00 26374386.00
Ops NUMA PTE updates 36624.00 55538.00
Ops NUMA PMD updates 54.00 51404.00
Ops NUMA hint faults 15504.00 75786.00
Ops NUMA hint local faults % 14860.00 56763.00
Ops NUMA hint local percent 95.85 74.90
Ops NUMA pages migrated 1629.00 6469222.00
Both the number of PTE updates and hint faults is dramatically
increased. While this is superficially unfortunate, it represents
ranges that were simply skipped without the patch. As a result
of the scanning and hinting faults, many more pages were also
migrated but as the time to completion is reduced, the overhead
is offset by the gain.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Raghavendra K T <raghavendra.kt@amd.com>
Link: https://lore.kernel.org/r/20231010083143.19593-7-mgorman@techsingularity.net
NUMA Balancing skips VMAs when the current task has not trapped a NUMA
fault within the VMA. If the VMA is skipped then mm->numa_scan_offset
advances and a task that is trapping faults within the VMA may never
fully update PTEs within the VMA.
Force tasks to update PTEs for partially scanned PTEs. The VMA will
be tagged for NUMA hints by some task but this removes some of the
benefit of tracking PID activity within a VMA. A follow-on patch
will mitigate this problem.
The test cases and machines evaluated did not trigger the corner case so
the performance results are neutral with only small changes within the
noise from normal test-to-test variance. However, the next patch makes
the corner case easier to trigger.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Raghavendra K T <raghavendra.kt@amd.com>
Link: https://lore.kernel.org/r/20231010083143.19593-6-mgorman@techsingularity.net
Recent NUMA hinting faulting activity is reset approximately every
VMA_PID_RESET_PERIOD milliseconds. However, if the current task has not
accessed a VMA then the reset check is missed and the reset is potentially
deferred forever. Check if the PID activity information should be reset
before checking if the current task recently trapped a NUMA hinting fault.
[ mgorman@techsingularity.net: Rewrite changelog ]
Suggested-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Raghavendra K T <raghavendra.kt@amd.com>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231010083143.19593-5-mgorman@techsingularity.net
NUMA balancing skips or scans VMAs for a variety of reasons. In preparation
for completing scans of VMAs regardless of PID access, trace the reasons
why a VMA was skipped. In a later patch, the tracing will be used to track
if a VMA was forcibly scanned.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231010083143.19593-4-mgorman@techsingularity.net
The access_pids[] field name is somewhat ambiguous as no PIDs are accessed.
Similarly, it's not clear that next_pid_reset is related to access_pids[].
Rename the fields to more accurately reflect their purpose.
[ mingo: Rename in the comments too. ]
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231010083143.19593-3-mgorman@techsingularity.net
Remove the rq::cpu_capacity_orig field and use arch_scale_cpu_capacity()
instead.
The scheduler uses 3 methods to get access to a CPU's max compute capacity:
- arch_scale_cpu_capacity(cpu) which is the default way to get a CPU's capacity.
- cpu_capacity_orig field which is periodically updated with
arch_scale_cpu_capacity().
- capacity_orig_of(cpu) which encapsulates rq->cpu_capacity_orig.
There is no real need to save the value returned by arch_scale_cpu_capacity()
in struct rq. arch_scale_cpu_capacity() returns:
- either a per_cpu variable.
- or a const value for systems which have only one capacity.
Remove rq::cpu_capacity_orig and use arch_scale_cpu_capacity() everywhere.
No functional changes.
Some performance tests on Arm64:
- small SMP device (hikey): no noticeable changes
- HMP device (RB5): hackbench shows minor improvement (1-2%)
- large smp (thx2): hackbench and tbench shows minor improvement (1%)
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/20231009103621.374412-2-vincent.guittot@linaro.org
find_new_ilb() returns nr_cpu_ids on failure - which is the usual
cpumask bitops return pattern, but is weird & unnecessary in this
context: not only is it a global variable, it it is a +1 out of
bounds CPU index and also has different signedness ...
Its only user, kick_ilb(), then checks the return against nr_cpu_ids
to decide to return. There's no other use.
So instead of this, use a standard -1 return on failure to find an
idle CPU, as the argument is signed already.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Link: https://lore.kernel.org/r/20231006102518.2452758-4-mingo@kernel.org
The old pick_eevdf() could fail to find the actual earliest eligible
deadline when it descended to the right looking for min_deadline, but
it turned out that that min_deadline wasn't actually eligible. In that
case we need to go back and search through any left branches we
skipped looking for the actual best _eligible_ min_deadline.
This is more expensive, but still O(log n), and at worst should only
involve descending two branches of the rbtree.
I've run this through a userspace stress test (thank you
tools/lib/rbtree.c), so hopefully this implementation doesn't miss any
corner cases.
Fixes: 147f3efaa241 ("sched/fair: Implement an EEVDF-like scheduling policy")
Signed-off-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/xm261qego72d.fsf_-_@google.com
Marek and Biju reported instances of:
"EEVDF scheduling fail, picking leftmost"
which Mike correlated with cgroup scheduling and the min_deadline heap
getting corrupted; some trace output confirms:
> And yeah, min_deadline is hosed somehow:
>
> validate_cfs_rq: --- /
> __print_se: ffff88845cf48080 w: 1024 ve: -58857638 lag: 870381 vd: -55861854 vmd: -66302085 E (11372/tr)
> __print_se: ffff88810d165800 w: 25 ve: -80323686 lag: 22336429 vd: -41496434 vmd: -66302085 E (-1//autogroup-31)
> __print_se: ffff888108379000 w: 25 ve: 0 lag: -57987257 vd: 114632828 vmd: 114632828 N (-1//autogroup-33)
> validate_cfs_rq: min_deadline: -55861854 avg_vruntime: -62278313462 / 1074 = -57987256
Turns out that reweight_entity(), which tries really hard to be fast,
does not do the normal dequeue+update+enqueue pattern but *does* scale
the deadline.
However, it then fails to propagate the updated deadline value up the
heap.
Fixes: 147f3efaa241 ("sched/fair: Implement an EEVDF-like scheduling policy")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reported-by: Biju Das <biju.das.jz@bp.renesas.com>
Reported-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Biju Das <biju.das.jz@bp.renesas.com>
Tested-by: Mike Galbraith <efault@gmx.de>
Link: https://lkml.kernel.org/r/20231006192445.GE743@noisy.programming.kicks-ass.net
The expectation is that placing a task at avg_vruntime() makes it
eligible. Turns out there is a corner case where this is not the case.
Specifically, avg_vruntime() relies on the fact that integer division
is a flooring function (eg. it discards the remainder). By this
property the value returned is slightly left of the true average.
However! when the average is a negative (relative to min_vruntime) the
effect is flipped and it becomes a ceil, with the result that the
returned value is just right of the average and thus not eligible.
Fixes: af4cf40470c2 ("sched/fair: Add cfs_rq::avg_vruntime")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tasks that never consume their full slice would not update their slice value.
This means that tasks that are spawned before the sysctl scaling keep their
original (UP) slice length.
Fixes: 147f3efaa241 ("sched/fair: Implement an EEVDF-like scheduling policy")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230915124822.847197830@noisy.programming.kicks-ass.net
It was useful to track feec() placement decision and debug the spare
capacity and optimization issues vs uclamp_max.
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230916232955.2099394-4-qyousef@layalina.io
find_energy_efficient_cpu() bails out early if effective util of the
task is 0 as the delta at this point will be zero and there's nothing
for EAS to do. When uclamp is being used, this could lead to wrong
decisions when uclamp_max is set to 0. In this case the task is capped
to performance point 0, but it is actually running and consuming energy
and we can benefit from EAS energy calculations.
Rework the condition so that it bails out when both util and uclamp_min
are 0.
We can do that without needing to use uclamp_task_util(); remove it.
Fixes: d81304bc6193 ("sched/uclamp: Cater for uclamp in find_energy_efficient_cpu()'s early exit condition")
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230916232955.2099394-3-qyousef@layalina.io
Linus Torvalds
Ingo Molnar
Vincent Guittot
Wang Jinchao
Pierre Gondois
Arnd Bergmann
Yiwei Lin
Peter Zijlstra
Abel Wu
Raghavendra K T
Keisuke Nishimura
Kefeng Wang
Yicong Yang
Barry Song
Joel Fernandes (Google)
Jiapeng Chong
Mel Gorman
Benjamin Segall
Qais Yousef