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Patch series "lib/stackdepot, kasan: fixes for stack eviction series", v3.
A few fixes for the stack depot eviction series ("stackdepot: allow
evicting stack traces").
This patch (of 5):
Stack depot functions can be called from various contexts that do
allocations, including with console locks taken. At the same time, stack
depot functions might print WARNING's or refcount-related failures.
This can cause a deadlock on console locks.
Add printk_deferred_enter/exit guards to stack depot to avoid this.
Link: https://lkml.kernel.org/r/cover.1703020707.git.andreyknvl@google.com
Link: https://lkml.kernel.org/r/82092f9040d075a161d1264377d51e0bac847e8a.1703020707.git.andreyknvl@google.com
Fixes: 108be8def4 ("lib/stackdepot: allow users to evict stack traces")
Fixes: cd11016e5f ("mm, kasan: stackdepot implementation. Enable stackdepot for SLAB")
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Closes: https://lore.kernel.org/all/000000000000f56750060b9ad216@google.com/
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Use the same splat markers as panic does for easier matching by external
tools scanning kernel dmesg for splats.
Link: https://lkml.kernel.org/r/20231218135339.23209-1-bp@alien8.de
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The last range stored in maple tree is typically quite large. By checking
if it exceeds the sum of the remaining ranges in that node, it is possible
to avoid checking all other gaps.
Running the maple tree test suite in user mode almost always results in a
near 100% hit rate for this optimization.
Link: https://lkml.kernel.org/r/20231215074632.82045-1-zhangpeng.00@bytedance.com
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Fix typos/grammar and spellos in documentation.
Link: https://lkml.kernel.org/r/20231210063839.29967-1-rdunlap@infradead.org
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Commit 0de56e38b3 ("maple_tree: use maple state end for write
operations") was broken by a later patch "maple_tree: do not preallocate
nodes for slot stores". But the later patch was scheduled ahead of
0de56e38b3, for 6.7-rc.
This fixlet undoes the damage.
Fixes: 0de56e38b3 ("maple_tree: use maple state end for write operations")
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mas_preallocate() defaults to requesting 1 node for preallocation and then
,depending on the type of store, will update the request variable. There
isn't a check for a slot store type, so slot stores are preallocating the
default 1 node. Slot stores do not require any additional nodes, so add a
check for the slot store case that will bypass node_count_gfp(). Update
the tests to reflect that slot stores do not require allocations.
User visible effects of this bug include increased memory usage from the
unneeded node that was allocated.
Link: https://lkml.kernel.org/r/20231213205058.386589-1-sidhartha.kumar@oracle.com
Fixes: 0b8bb544b1 ("maple_tree: update mas_preallocate() testing")
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Cc: <stable@vger.kernel.org> [6.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mas_split_final_node() always returns true and its return value is never
checked.
Change return type to void.
Link: https://lkml.kernel.org/r/20231109160821.16248-2-ppbuk5246@gmail.com
Signed-off-by: Levi Yun <ppbuk5246@gmail.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Now it seems that the incoming 'end' is already pointing to the last item,
so we can simplify this function, considering only whether the last slot
is being used. This has passed the maple tree test suite.
Link: https://lkml.kernel.org/r/20231120070937.35481-6-zhangpeng.00@bytedance.com
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
There are two identical checks, delete one of them.
Link: https://lkml.kernel.org/r/20231120070937.35481-5-zhangpeng.00@bytedance.com
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The parameter maple_type is not used, so remove it.
Link: https://lkml.kernel.org/r/20231120070937.35481-4-zhangpeng.00@bytedance.com
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When the child node is the first child of its parent node, mas->min does
not need to be updated. This can reduce the number of ascending times
in some cases.
Link: https://lkml.kernel.org/r/20231120070937.35481-3-zhangpeng.00@bytedance.com
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The function are defined in the maple_tree.c file, but not called
elsewhere, so delete the unused function.
lib/maple_tree.c:689:29: warning: unused function 'mas_pivot'.
Link: https://lkml.kernel.org/r/20231027084944.24888-1-jiapeng.chong@linux.alibaba.com
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=7064
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mtree_range_walk() needed to be updated to avoid checking if there was a
pivot value. On closer examination, the code could avoid setting min or
max in certain scenarios. The commit removes the extra check for
pivot[offset] before setting max and only sets max when necessary. It
also only sets min if it is necessary by checking offset 0 prior to the
loop (as it has always done).
The commit also drops a dead node check since the end of the node will
return the array size when the last slot is occupied (by a potential reuse
in a dead node). The data will be discarded later if the node is marked
dead.
Benchmarking these changes results in an increase in performance of 5.45%
using the BENCH_WALK in the maple tree test code.
Link: https://lkml.kernel.org/r/20231101171629.3612299-13-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Since the pivot being set is now reliable, the optimized loop no longer
needs to find the node end. The redundant check for a dead node can also
be avoided as there is no danger of using the wrong pivot since the
results will be thrown out in the case of a dead node by the later check.
This patch also adds a benchmark test for the function to the maple tree
test framework. The benchmark shows an average increase performance of
5.98% over 3 runs with this commit.
Link: https://lkml.kernel.org/r/20231101171629.3612299-12-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
ma_wr_state was previously tracking the end of the node for writing.
Since the implementation of the ma_state end tracking, this is duplicated
work. This patch removes the maple write state tracking of the end of the
node and uses the maple state end instead.
Link: https://lkml.kernel.org/r/20231101171629.3612299-11-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Now that the status of the maple state is outside of the node, the
mas_searchable() function can be dropped for easier open-coding of what is
going on.
Link: https://lkml.kernel.org/r/20231101171629.3612299-10-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
There are a few functions which were inlined but are somewhat too large to
inline, so remove the inline key word.
There are also several very small functions which are used in critical
code sections which gcc was not inlining, so make this more strict and use
__always_line for these functions.
Link: https://lkml.kernel.org/r/20231101171629.3612299-8-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The node end is set during the walk, so use the resulting end instead of
re-fetching it.
Link: https://lkml.kernel.org/r/20231101171629.3612299-7-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When looking for the next entry, don't recalculate the node end as it is
now tracked in the maple state.
Link: https://lkml.kernel.org/r/20231101171629.3612299-6-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Analysis of the mas_for_each() iteration showed that there is a
significant time spent finding the end of a node. This time can be
greatly reduced if the end of the node is cached in the maple state. Care
must be taken to update & invalidate as necessary.
Link: https://lkml.kernel.org/r/20231101171629.3612299-5-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mas_erase() may not deal correctly with all maple states. Make the
function more robust by ensuring the state is in one of the two acceptable
states.
Link: https://lkml.kernel.org/r/20231101171629.3612299-3-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Peng Zhang <zhangpeng.00@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "maple_tree: iterator state changes".
These patches have some general cleanup and a change to separate the maple
state status tracking from the maple state node.
The maple state status change allows for walks to continue from previous
places when the status needs to be recorded to make logical sense for the
next call to the maple state. For instance, it allows for prev/next to
function in a way that better resembles the linked list. It also allows
switch statements to be used to detect missed states during compile, and
the addition of fast-path "active" state is cleaner as an enum.
While making the status change, perf showed some very small (one line)
functions that were not inlined even with the inline key word. Making
these small functions __always_inline is less expensive according to perf.
As part of that change, some inlines have been dropped from larger
functions.
Perf also showed that the commonly used mas_for_each() iterator was
spending a lot of time finding the end of the node. This series
introduces caching of the end of the node in the maple state (and updating
it during writes). This caching along with the inline changes yielded at
23.25% improvement on the BENCH_MAS_FOR_EACH maple tree test framework
benchmark.
I've also included a change to mtree_range_walk and mtree_lookup_walk to
take advantage of Peng's change [1] to the initial pivot setup.
mmtests did not produce any significant gains.
[1] https://lore.kernel.org/all/20230711035444.526-1-zhangpeng.00@bytedance.com/T/#u
This patch (of 12):
Removing the default types from the switch statements will cause compile
warnings on missing cases.
Link: https://lkml.kernel.org/r/20231101171629.3612299-2-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Record and report more information to help us find the cause of the bug
and to help us correlate the error with other system events.
This patch adds recording and showing CPU number and timestamp at
allocation and free (controlled by CONFIG_KASAN_EXTRA_INFO). The
timestamps in the report use the same format and source as printk.
Error occurrence timestamp is already implicit in the printk log, and CPU
number is already shown by dump_stack_lvl, so there is no need to add it.
In order to record CPU number and timestamp at allocation and free,
corresponding members need to be added to the relevant data structures,
which will lead to increased memory consumption.
In Generic KASAN, members are added to struct kasan_track. Since in most
cases, alloc meta is stored in the redzone and free meta is stored in the
object or the redzone, memory consumption will not increase much.
In SW_TAGS KASAN and HW_TAGS KASAN, members are added to struct
kasan_stack_ring_entry. Memory consumption increases as the size of
struct kasan_stack_ring_entry increases (this part of the memory is
allocated by memblock), but since this is configurable, it is up to the
user to choose.
Link: https://lkml.kernel.org/r/VI1P193MB0752BD991325D10E4AB1913599BDA@VI1P193MB0752.EURP193.PROD.OUTLOOK.COM
Signed-off-by: Juntong Deng <juntong.deng@outlook.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
KMSAN is frequently used in fuzzing scenarios and thus saves a lot of
stack traces. As KMSAN does not support evicting stack traces from the
stack depot, the stack depot capacity might be reached quickly with large
stack records.
Adjust the maximum number of stack depot pools for this case.
The average size of a stack trace saved into the stack depot is ~16
frames. Thus, adjust the maximum pools number accordingly to keep the
maximum number of stack traces that can be saved into the stack depot
similar to the one that was allowed before the stack trace eviction
changes.
Link: https://lkml.kernel.org/r/301a115cf7ce8ddb42ef6de9151c2bb76ba728fc.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add stack_depot_put, a function that decrements the reference counter on a
stack record and removes it from the stack depot once the counter reaches
0.
Internally, when removing a stack record, the function unlinks it from the
hash table bucket and returns to the freelist.
With this change, the users of stack depot can call stack_depot_put when
keeping a stack trace in the stack depot is not needed anymore. This
allows avoiding polluting the stack depot with irrelevant stack traces and
thus have more space to store the relevant ones before the stack depot
reaches its capacity.
Link: https://lkml.kernel.org/r/1d1ad5692ee43d4fc2b3fd9d221331d30b36123f.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add a reference counter for how many times a stack records has been
added to stack depot.
Add a new STACK_DEPOT_FLAG_GET flag to stack_depot_save_flags that
instructs the stack depot to increment the refcount.
Do not yet decrement the refcount; this is implemented in one of the
following patches.
Do not yet enable any users to use the flag to avoid overflowing the
refcount.
This is preparatory patch for implementing the eviction of stack records
from the stack depot.
Link: https://lkml.kernel.org/r/a3fc14a2359d019d2a008d4ff8b46a665371ffee.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Change the bool can_alloc argument of __stack_depot_save to a u32
argument that accepts a set of flags.
The following patch will add another flag to stack_depot_save_flags
besides the existing STACK_DEPOT_FLAG_CAN_ALLOC.
Also rename the function to stack_depot_save_flags, as
__stack_depot_save is a cryptic name,
Link: https://lkml.kernel.org/r/645fa15239621eebbd3a10331e5864b718839512.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Switch stack_record to use list_head for links in the hash table and in
the freelist.
This will allow removing entries from the hash table buckets.
This is preparatory patch for implementing the eviction of stack records
from the stack depot.
Link: https://lkml.kernel.org/r/4787d9a584cd33433d9ee1846b17fa3d3e1987ad.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Currently, stack depot uses the following locking scheme:
1. Lock-free accesses when looking up a stack record, which allows to
have multiple users to look up records in parallel;
2. Spinlock for protecting the stack depot pools and the hash table
when adding a new record.
For implementing the eviction of stack traces from stack depot, the
lock-free approach is not going to work anymore, as we will need to be
able to also remove records from the hash table.
Convert the spinlock into a read/write lock, and drop the atomic
accesses, as they are no longer required.
Looking up stack traces is now protected by the read lock and adding new
records - by the write lock. One of the following patches will add a
new function for evicting stack records, which will be protected by the
write lock as well.
With this change, multiple users can still look up records in parallel.
This is preparatory patch for implementing the eviction of stack records
from the stack depot.
Link: https://lkml.kernel.org/r/9f81ffcc4bb422ebb6326a65a770bf1918634cbb.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Instead of using the global pool_offset variable to find a free slot when
storing a new stack record, mainlain a freelist of free slots within the
allocated stack pools.
A global next_stack variable is used as the head of the freelist, and the
next field in the stack_record struct is reused as freelist link (when the
record is not in the freelist, this field is used as a link in the hash
table).
This is preparatory patch for implementing the eviction of stack records
from the stack depot.
Link: https://lkml.kernel.org/r/b9e4c79955c2121b69301778643b203d3fb09ccc.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Instead of using the last pointer in stack_pools for storing the pointer
to a new pool (which does not yet store any stack records), use a new
new_pool variable.
This a purely code readability change: it seems more logical to store the
pointer to a pool with a special meaning in a dedicated variable.
Link: https://lkml.kernel.org/r/448bc18296c16bef95cb3167697be6583dcc8ce3.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Rename next_pool_required to new_pool_required.
This a purely code readability change: the following patch will change
stack depot to store the pointer to the new pool in a separate variable,
and "new" seems like a more logical name.
Link: https://lkml.kernel.org/r/fd7cd6c6eb250c13ec5d2009d75bb4ddd1470db9.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Split code in depot_alloc_stack and depot_init_pool into 3 functions:
1. depot_keep_next_pool that keeps preallocated memory for the next pool
if required.
2. depot_update_pools that moves on to the next pool if there's no space
left in the current pool, uses preallocated memory for the new current
pool if required, and calls depot_keep_next_pool otherwise.
3. depot_alloc_stack that calls depot_update_pools and then allocates
a stack record as before.
This makes it somewhat easier to follow the logic of depot_alloc_stack and
also serves as a preparation for implementing the eviction of stack
records from the stack depot.
Link: https://lkml.kernel.org/r/71fb144d42b701fcb46708d7f4be6801a4a8270e.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Drop smp_load_acquire from next_pool_required in depot_init_pool, as both
depot_init_pool and the all smp_store_release's to this variable are
executed under the stack depot lock.
Also simplify and clean up comments accompanying the use of atomic
accesses in the stack depot code.
Link: https://lkml.kernel.org/r/c118ef044d8db80248d9e1f14592c72e8429e9d9.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Instead of storing stack records in stack depot pools one right after
another, use fixed-sized slots.
Add a new Kconfig option STACKDEPOT_MAX_FRAMES that allows to select the
size of the slot in frames. Use 64 as the default value, which is the
maximum stack trace size both KASAN and KMSAN use right now.
Also add descriptions for other stack depot Kconfig options.
This is preparatory patch for implementing the eviction of stack records
from the stack depot.
Link: https://lkml.kernel.org/r/dce7d030a99ff61022509665187fac45b0827298.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add a helper depot_fetch_stack function that fetches the pointer to a
stack record.
With this change, all static depot_* functions now operate on stack pools
and the exported stack_depot_* functions operate on the hash table.
Link: https://lkml.kernel.org/r/170d8c202f29dc8e3d5491ee074d1e9e029a46db.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Stack depot doesn't use the valid bit in handles in any way, so drop it.
Link: https://lkml.kernel.org/r/34969bba2ca6e012c6ad071767197dee64dc5723.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The retval local variable in __stack_depot_save has the union type
handle_parts, but the function never uses anything but the union's handle
field.
Define retval simply as depot_stack_handle_t to simplify the code.
Link: https://lkml.kernel.org/r/3b0763c8057a1cf2f200ff250a5f9580ee36a28c.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Do not try fetching a stack trace from the stack depot if the
stack_depot_disabled flag is enabled.
Link: https://lkml.kernel.org/r/c3bfa3b7ab00b2e48ab75a3fbb9c67555777cb08.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "stackdepot: allow evicting stack traces", v4.
Currently, the stack depot grows indefinitely until it reaches its
capacity. Once that happens, the stack depot stops saving new stack
traces.
This creates a problem for using the stack depot for in-field testing and
in production.
For such uses, an ideal stack trace storage should:
1. Allow saving fresh stack traces on systems with a large uptime while
limiting the amount of memory used to store the traces;
2. Have a low performance impact.
Implementing #1 in the stack depot is impossible with the current
keep-forever approach. This series targets to address that. Issue #2 is
left to be addressed in a future series.
This series changes the stack depot implementation to allow evicting
unneeded stack traces from the stack depot. The users of the stack depot
can do that via new stack_depot_save_flags(STACK_DEPOT_FLAG_GET) and
stack_depot_put APIs.
Internal changes to the stack depot code include:
1. Storing stack traces in fixed-frame-sized slots (vs precisely-sized
slots in the current implementation); the slot size is controlled via
CONFIG_STACKDEPOT_MAX_FRAMES (default: 64 frames);
2. Keeping available slots in a freelist (vs keeping an offset to the next
free slot);
3. Using a read/write lock for synchronization (vs a lock-free approach
combined with a spinlock).
This series also integrates the eviction functionality into KASAN: the
tag-based modes evict stack traces when the corresponding entry leaves the
stack ring, and Generic KASAN evicts stack traces for objects once those
leave the quarantine.
With KASAN, despite wasting some space on rounding up the size of each
stack record, the total memory consumed by stack depot gets saturated due
to the eviction of irrelevant stack traces from the stack depot.
With the tag-based KASAN modes, the average total amount of memory used
for stack traces becomes ~0.5 MB (with the current default stack ring size
of 32k entries and the default CONFIG_STACKDEPOT_MAX_FRAMES of 64). With
Generic KASAN, the stack traces take up ~1 MB per 1 GB of RAM (as the
quarantine's size depends on the amount of RAM).
However, with KMSAN, the stack depot ends up using ~4x more memory per a
stack trace than before. Thus, for KMSAN, the stack depot capacity is
increased accordingly. KMSAN uses a lot of RAM for shadow memory anyway,
so the increased stack depot memory usage will not make a significant
difference.
Other users of the stack depot do not save stack traces as often as KASAN
and KMSAN. Thus, the increased memory usage is taken as an acceptable
trade-off. In the future, these other users can take advantage of the
eviction API to limit the memory waste.
There is no measurable boot time performance impact of these changes for
KASAN on x86-64. I haven't done any tests for arm64 modes (the stack
depot without performance optimizations is not suitable for intended use
of those anyway), but I expect a similar result. Obtaining and copying
stack trace frames when saving them into stack depot is what takes the
most time.
This series does not yet provide a way to configure the maximum size of
the stack depot externally (e.g. via a command-line parameter). This
will be added in a separate series, possibly together with the performance
improvement changes.
This patch (of 22):
Currently, if stack_depot_disable=off is passed to the kernel command-line
after stack_depot_disable=on, stack depot prints a message that it is
disabled, while it is actually enabled.
Fix this by moving printing the disabled message to
stack_depot_early_init. Place it before the
__stack_depot_early_init_requested check, so that the message is printed
even if early stack depot init has not been requested.
Also drop the stack_table = NULL assignment from disable_stack_depot, as
stack_table is NULL by default.
Link: https://lkml.kernel.org/r/cover.1700502145.git.andreyknvl@google.com
Link: https://lkml.kernel.org/r/73a25c5fff29f3357cd7a9330e85e09bc8da2cbe.1700502145.git.andreyknvl@google.com
Fixes: e1fdc40334 ("lib: stackdepot: add support to disable stack depot")
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
KASan inline instrumentation can yield up to a 2x performance gain at the
cost of a larger binary.
Make inline instrumentation the default, as suggested in the bug report
below.
When an architecture does not support inline instrumentation, it should
set ARCH_DISABLE_KASAN_INLINE, as done by PowerPC, for instance.
Link: https://lkml.kernel.org/r/20231109155101.186028-1-paul.heidekrueger@tum.de
Signed-off-by: Paul Heidekrüger <paul.heidekrueger@tum.de>
Reported-by: Andrey Konovalov <andreyknvl@gmail.com>
Reviewed-by: Marco Elver <elver@google.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=203495
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When destroying maple tree, preserve its attributes and then turn it into
an empty tree. This allows it to be reused without needing to be
reinitialized.
Link: https://lkml.kernel.org/r/20231027033845.90608-10-zhangpeng.00@bytedance.com
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Mike Christie <michael.christie@oracle.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Updated check_forking() and bench_forking() to use __mt_dup() to duplicate
maple tree.
Link: https://lkml.kernel.org/r/20231027033845.90608-9-zhangpeng.00@bytedance.com
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Mike Christie <michael.christie@oracle.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Skip other tests when BENCH is enabled so that performance can be measured
in user space.
Link: https://lkml.kernel.org/r/20231027033845.90608-8-zhangpeng.00@bytedance.com
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Mike Christie <michael.christie@oracle.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Introduce interfaces __mt_dup() and mtree_dup(), which are used to
duplicate a maple tree. They duplicate a maple tree in Depth-First Search
(DFS) pre-order traversal. It uses memcopy() to copy nodes in the source
tree and allocate new child nodes in non-leaf nodes. The new node is
exactly the same as the source node except for all the addresses stored in
it. It will be faster than traversing all elements in the source tree and
inserting them one by one into the new tree. The time complexity of these
two functions is O(n).
The difference between __mt_dup() and mtree_dup() is that mtree_dup()
handles locks internally.
Analysis of the average time complexity of this algorithm:
For simplicity, let's assume that the maximum branching factor of all
non-leaf nodes is 16 (in allocation mode, it is 10), and the tree is a
full tree.
Under the given conditions, if there is a maple tree with n elements, the
number of its leaves is n/16. From bottom to top, the number of nodes in
each level is 1/16 of the number of nodes in the level below. So the
total number of nodes in the entire tree is given by the sum of n/16 +
n/16^2 + n/16^3 + ... + 1. This is a geometric series, and it has log(n)
terms with base 16. According to the formula for the sum of a geometric
series, the sum of this series can be calculated as (n-1)/15. Each node
has only one parent node pointer, which can be considered as an edge. In
total, there are (n-1)/15-1 edges.
This algorithm consists of two operations:
1. Traversing all nodes in DFS order.
2. For each node, making a copy and performing necessary modifications
to create a new node.
For the first part, DFS traversal will visit each edge twice. Let
T(ascend) represent the cost of taking one step downwards, and T(descend)
represent the cost of taking one step upwards. And both of them are
constants (although mas_ascend() may not be, as it contains a loop, but
here we ignore it and treat it as a constant). So the time spent on the
first part can be represented as ((n-1)/15-1) * (T(ascend) + T(descend)).
For the second part, each node will be copied, and the cost of copying a
node is denoted as T(copy_node). For each non-leaf node, it is necessary
to reallocate all child nodes, and the cost of this operation is denoted
as T(dup_alloc). The behavior behind memory allocation is complex and not
specific to the maple tree operation. Here, we assume that the time
required for a single allocation is constant. Since the size of a node is
fixed, both of these symbols are also constants. We can calculate that
the time spent on the second part is ((n-1)/15) * T(copy_node) + ((n-1)/15
- n/16) * T(dup_alloc).
Adding both parts together, the total time spent by the algorithm can be
represented as:
((n-1)/15) * (T(ascend) + T(descend) + T(copy_node) + T(dup_alloc)) -
n/16 * T(dup_alloc) - (T(ascend) + T(descend))
Let C1 = T(ascend) + T(descend) + T(copy_node) + T(dup_alloc)
Let C2 = T(dup_alloc)
Let C3 = T(ascend) + T(descend)
Finally, the expression can be simplified as:
((16 * C1 - 15 * C2) / (15 * 16)) * n - (C1 / 15 + C3).
This is a linear function, so the average time complexity is O(n).
Link: https://lkml.kernel.org/r/20231027033845.90608-4-zhangpeng.00@bytedance.com
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Suggested-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Mike Christie <michael.christie@oracle.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "Introduce __mt_dup() to improve the performance of fork()", v7.
This series introduces __mt_dup() to improve the performance of fork().
During the duplication process of mmap, all VMAs are traversed and
inserted one by one into the new maple tree, causing the maple tree to be
rebalanced multiple times. Balancing the maple tree is a costly
operation. To duplicate VMAs more efficiently, mtree_dup() and __mt_dup()
are introduced for the maple tree. They can efficiently duplicate a maple
tree.
Here are some algorithmic details about {mtree,__mt}_dup(). We perform a
DFS pre-order traversal of all nodes in the source maple tree. During
this process, we fully copy the nodes from the source tree to the new
tree. This involves memory allocation, and when encountering a new node,
if it is a non-leaf node, all its child nodes are allocated at once.
This idea was originally from Liam R. Howlett's Maple Tree Work email,
and I added some of my own ideas to implement it. Some previous
discussions can be found in [1]. For a more detailed analysis of the
algorithm, please refer to the logs for patch [3/10] and patch [10/10].
There is a "spawn" in byte-unixbench[2], which can be used to test the
performance of fork(). I modified it slightly to make it work with
different number of VMAs.
Below are the test results. The first row shows the number of VMAs. The
second and third rows show the number of fork() calls per ten seconds,
corresponding to next-20231006 and the this patchset, respectively. The
test results were obtained with CPU binding to avoid scheduler load
balancing that could cause unstable results. There are still some
fluctuations in the test results, but at least they are better than the
original performance.
21 121 221 421 821 1621 3221 6421 12821 25621 51221
112100 76261 54227 34035 20195 11112 6017 3161 1606 802 393
114558 83067 65008 45824 28751 16072 8922 4747 2436 1233 599
2.19% 8.92% 19.88% 34.64% 42.37% 44.64% 48.28% 50.17% 51.68% 53.74% 52.42%
Thanks to Liam and Matthew for the review.
This patch (of 10):
Add two helpers:
1. mt_free_one(), used to free a maple node.
2. mt_attr(), used to obtain the attributes of maple tree.
Link: https://lkml.kernel.org/r/20231027033845.90608-1-zhangpeng.00@bytedance.com
Link: https://lkml.kernel.org/r/20231027033845.90608-2-zhangpeng.00@bytedance.com
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Mike Christie <michael.christie@oracle.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
