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d119357d07
linux/kernel
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Paul E. McKenney d119357d07 rcu-tasks: Treat only synchronous grace periods urgently 
The performance requirements on RCU Tasks, and in particular on RCU
Tasks Trace, have evolved over time as the workloads have evolved.
The current implementation is designed to provide low grace-period
latencies, and also to accommodate short-duration floods of callbacks.

However, current workloads can also provide a constant background
callback-queuing rate of a few hundred call_rcu_tasks_trace() invocations
per second.  This results in continuous back-to-back RCU Tasks Trace
grace periods, which in turn can consume the better part of 10% of a CPU.
One could take the attitude that there are several tens of other CPUs on
the systems running such workloads, but energy efficiency is a thing.
On these systems, although asynchronous grace-period requests happen
every few milliseconds, synchronous grace-period requests are quite rare.

This commit therefore arrranges for grace periods to be initiated
immediately in response to calls to synchronize_rcu_tasks*() and
also to calls to synchronize_rcu_mult() that are passed one of the
call_rcu_tasks*() functions.  These are recognized by the tell-tale
wakeme_after_rcu callback function.

In other cases, callbacks are gathered up for up to about 250 milliseconds
before a grace period is initiated.  This results in more than an order of
magnitude reduction in RCU Tasks Trace grace periods, with corresponding
reduction in consumption of CPU time.

Reported-by: Alexei Starovoitov <ast@kernel.org>
Reported-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2023-07-14 15:00:11 -07:00
..
bpf bpf, btf: Warn but return no error for NULL btf from __register_btf_kfunc_id_set() 2023-07-03 18:48:09 +02:00
cgroup - Yosry Ahmed brought back some cgroup v1 stats in OOM logs. 2023-06-28 10:28:11 -07:00
configs mm/slab: rename CONFIG_SLAB to CONFIG_SLAB_DEPRECATED 2023-05-26 19:01:47 +02:00
debug kdb: move kdb_send_sig() declaration to a better header file 2023-07-03 09:27:12 +01:00
dma dma-mapping fixes for Linux 6.5 2023-07-09 10:24:22 -07:00
entry ptrace: Provide set/get interface for syscall user dispatch 2023-04-16 14:23:07 +02:00
events cxl for v6.5 2023-07-01 08:58:41 -07:00
futex - Prevent the leaking of a debug timer in futex_waitv() 2023-01-01 11:15:05 -08:00
gcov gcov: add support for checksum field 2022-12-21 14:31:52 -08:00
irq irqdomain: Use return value of strreplace() 2023-06-30 11:13:44 +02:00
kcsan kcsan: Don't expect 64 bits atomic builtins from 32 bits architectures 2023-06-09 23:29:50 +10:00
livepatch livepatch: Make 'klp_stack_entries' static 2023-06-05 13:56:52 +02:00
locking - Arnd Bergmann has fixed a bunch of -Wmissing-prototypes in 2023-06-28 10:59:38 -07:00
module module: fix init_module_from_file() error handling 2023-07-04 10:17:11 -07:00
power - Yosry Ahmed brought back some cgroup v1 stats in OOM logs. 2023-06-28 10:28:11 -07:00
printk seqlock/latch: Provide raw_read_seqcount_latch_retry() 2023-06-05 21:11:03 +02:00
rcu rcu-tasks: Treat only synchronous grace periods urgently 2023-07-14 15:00:11 -07:00
sched cgroup: Changes for v6.5 2023-06-27 16:54:21 -07:00
time hardening updates for v6.5-rc1 2023-06-27 21:24:18 -07:00
trace Tracing fixes for 6.5: 2023-07-06 19:07:15 -07:00
.gitignore
acct.c acct: fix potential integer overflow in encode_comp_t() 2022-11-30 16:13:18 -08:00
async.c
audit_fsnotify.c audit: fix potential double free on error path from fsnotify_add_inode_mark 2022-08-22 18:50:06 -04:00
audit_tree.c
audit_watch.c audit_init_parent(): constify path 2022-09-01 17:39:30 -04:00
audit.c audit: use time_after to compare time 2022-08-29 19:47:03 -04:00
audit.h audit: avoid missing-prototype warnings 2023-05-17 11:34:55 -04:00
auditfilter.c
auditsc.c capability: just use a 'u64' instead of a 'u32[2]' array 2023-03-01 10:01:22 -08:00
backtracetest.c
bounds.c mm: multi-gen LRU: minimal implementation 2022-09-26 19:46:09 -07:00
capability.c capability: fix kernel-doc warnings in capability.c 2023-05-22 14:30:52 -04:00
cfi.c cfi: Switch to -fsanitize=kcfi 2022-09-26 10:13:13 -07:00
compat.c sched_getaffinity: don't assume 'cpumask_size()' is fully initialized 2023-03-14 19:32:38 -07:00
configs.c
context_tracking.c locking/atomic: treewide: use raw_atomic*_<op>() 2023-06-05 09:57:20 +02:00
cpu_pm.c cpuidle, cpu_pm: Remove RCU fiddling from cpu_pm_{enter,exit}() 2023-01-13 11:48:15 +01:00
cpu.c cpu/hotplug: Fix off by one in cpuhp_bringup_mask() 2023-05-23 18:06:40 +02:00
crash_core.c mm, treewide: redefine MAX_ORDER sanely 2023-04-05 19:42:46 -07:00
crash_dump.c
cred.c cred: Do not default to init_cred in prepare_kernel_cred() 2022-11-01 10:04:52 -07:00
delayacct.c delayacct: track delays from IRQ/SOFTIRQ 2023-04-18 16:39:34 -07:00
dma.c
exec_domain.c
exit.c fork, vhost: Use CLONE_THREAD to fix freezer/ps regression 2023-06-01 17:15:33 -04:00
extable.c context_tracking: Take NMI eqs entrypoints over RCU 2022-07-05 13:32:59 -07:00
fail_function.c kernel/fail_function: fix memory leak with using debugfs_lookup() 2023-02-08 13:36:22 +01:00
fork.c fork: lock VMAs of the parent process when forking 2023-07-08 14:08:02 -07:00
freezer.c freezer,sched: Rewrite core freezer logic 2022-09-07 21:53:50 +02:00
gen_kheaders.sh Revert "kheaders: substituting --sort in archive creation" 2023-05-28 16:20:21 +09:00
groups.c security: Add LSM hook to setgroups() syscall 2022-07-15 18:21:49 +00:00
hung_task.c kernel/hung_task.c: set some hung_task.c variables storage-class-specifier to static 2023-04-08 13:45:37 -07:00
iomem.c
irq_work.c trace: Add trace_ipi_send_cpu() 2023-03-24 11:01:29 +01:00
jump_label.c jump_label: Prevent key->enabled int overflow 2022-12-01 15:53:05 -08:00
kallsyms_internal.h kallsyms: Reduce the memory occupied by kallsyms_seqs_of_names[] 2022-11-12 18:47:36 -08:00
kallsyms_selftest.c kallsyms: Delete an unused parameter related to {module_}kallsyms_on_each_symbol() 2023-03-19 13:27:19 -07:00
kallsyms_selftest.h kallsyms: Add self-test facility 2022-11-15 00:42:02 -08:00
kallsyms.c v6.5-rc1-modules-next 2023-06-28 15:51:08 -07:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c kcov: add prototypes for helper functions 2023-06-09 17:44:17 -07:00
kexec_core.c kexec: enable kexec_crash_size to support two crash kernel regions 2023-06-09 17:44:24 -07:00
kexec_elf.c
kexec_file.c - Arnd Bergmann has fixed a bunch of -Wmissing-prototypes in 2023-06-28 10:59:38 -07:00
kexec_internal.h panic, kexec: make __crash_kexec() NMI safe 2022-09-11 21:55:06 -07:00
kexec.c kexec: introduce sysctl parameters kexec_load_limit_* 2023-02-02 22:50:05 -08:00
kheaders.c kheaders: Use array declaration instead of char 2023-03-24 20:10:59 -07:00
kprobes.c fprobe: Pass return address to the handlers 2023-06-06 21:39:55 +09:00
ksyms_common.c kallsyms: make kallsyms_show_value() as generic function 2023-06-08 12:27:20 -07:00
ksysfs.c kernel/ksysfs.c: use sysfs_emit for sysfs show handlers 2023-03-24 17:09:14 +01:00
kthread.c - Arnd Bergmann has fixed a bunch of -Wmissing-prototypes in 2023-06-28 10:59:38 -07:00
latencytop.c latencytop: use the last element of latency_record of system 2022-09-11 21:55:12 -07:00
Makefile v6.5-rc1-modules-next 2023-06-28 15:51:08 -07:00
module_signature.c
notifier.c notifiers: add tracepoints to the notifiers infrastructure 2023-04-08 13:45:38 -07:00
nsproxy.c convert setns(2) to fdget()/fdput() 2023-04-20 22:55:35 -04:00
padata.c padata: use alignment when calculating the number of worker threads 2023-03-14 17:06:44 +08:00
panic.c panic: hide unused global functions 2023-06-09 17:44:15 -07:00
params.c kallsyms: Replace all non-returning strlcpy with strscpy 2023-06-14 12:27:38 -07:00
pid_namespace.c pid: use struct_size_t() helper 2023-07-01 08:26:23 -07:00
pid_sysctl.h kernel: pid_namespace: remove unused set_memfd_noexec_scope() 2023-06-19 16:19:28 -07:00
pid.c pid: use struct_size_t() helper 2023-07-01 08:26:23 -07:00
profile.c kernel/profile.c: simplify duplicated code in profile_setup() 2022-09-11 21:55:12 -07:00
ptrace.c ptrace: Provide set/get interface for syscall user dispatch 2023-04-16 14:23:07 +02:00
range.c
reboot.c kernel/reboot: Add SYS_OFF_MODE_RESTART_PREPARE mode 2022-10-04 15:59:36 +02:00
regset.c
relay.c relayfs: fix out-of-bounds access in relay_file_read 2023-05-02 17:23:27 -07:00
resource_kunit.c
resource.c dax/kmem: Fix leak of memory-hotplug resources 2023-02-17 14:58:01 -08:00
rseq.c rseq: Extend struct rseq with per-memory-map concurrency ID 2022-12-27 12:52:12 +01:00
scftorture.c
scs.c scs: add support for dynamic shadow call stacks 2022-11-09 18:06:35 +00:00
seccomp.c seccomp: simplify sysctls with register_sysctl_init() 2023-04-13 11:49:20 -07:00
signal.c v6.5-rc1-sysctl-next 2023-06-28 16:05:21 -07:00
smp.c trace,smp: Add tracepoints for scheduling remotelly called functions 2023-06-16 22:08:09 +02:00
smpboot.c cpu/hotplug: Remove unused state functions 2023-05-15 13:45:00 +02:00
smpboot.h
softirq.c Revert "softirq: Let ksoftirqd do its job" 2023-05-09 21:50:27 +02:00
stackleak.c stackleak: allow to specify arch specific stackleak poison function 2023-04-20 11:36:35 +02:00
stacktrace.c
static_call_inline.c static_call: Add call depth tracking support 2022-10-17 16:41:16 +02:00
static_call.c
stop_machine.c
sys_ni.c asm-generic updates for 6.5 2023-07-06 10:06:04 -07:00
sys.c riscv: Add prctl controls for userspace vector management 2023-06-08 07:16:53 -07:00
sysctl-test.c kernel/sysctl-test: use SYSCTL_{ZERO/ONE_HUNDRED} instead of i_{zero/one_hundred} 2022-09-08 16:56:45 -07:00
sysctl.c v6.5-rc1-sysctl-next 2023-06-28 16:05:21 -07:00
task_work.c task_work: use try_cmpxchg in task_work_add, task_work_cancel_match and task_work_run 2022-09-11 21:55:10 -07:00
taskstats.c genetlink: start to validate reserved header bytes 2022-08-29 12:47:15 +01:00
torture.c torture: Fix hang during kthread shutdown phase 2023-01-05 12:10:35 -08:00
tracepoint.c tracepoint: Allow livepatch module add trace event 2023-02-18 14:34:36 -05:00
tsacct.c
ucount.c
uid16.c
uid16.h
umh.c sysctl: fix unused proc_cap_handler() function warning 2023-06-29 15:19:43 -07:00
up.c
user_namespace.c userns: fix a struct's kernel-doc notation 2023-02-02 22:50:04 -08:00
user-return-notifier.c
user.c kernel/user: Allow user_struct::locked_vm to be usable for iommufd 2022-11-30 20:16:49 -04:00
usermode_driver.c
utsname_sysctl.c utsname: simplify one-level sysctl registration for uts_kern_table 2023-04-13 11:49:35 -07:00
utsname.c
vhost_task.c vhost: Fix worker hangs due to missed wake up calls 2023-06-08 15:43:09 -04:00
watch_queue.c watch_queue: prevent dangling pipe pointer 2023-06-06 10:47:04 +02:00
watchdog_buddy.c watchdog/hardlockup: move SMP barriers from common code to buddy code 2023-06-19 16:25:28 -07:00
watchdog_perf.c watchdog/perf: add a weak function for an arch to detect if perf can use NMIs 2023-06-09 17:44:21 -07:00
watchdog.c watchdog/sparc64: define HARDLOCKUP_DETECTOR_SPARC64 2023-06-19 16:25:29 -07:00
workqueue_internal.h workqueue: Automatically mark CPU-hogging work items CPU_INTENSIVE 2023-05-17 17:02:08 -10:00
workqueue.c workqueue: Changes for v6.5 2023-06-27 16:32:52 -07:00