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alloc_tag: avoid current->alloc_tag manipulations when profiling is disabled

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When memory allocation profiling is disabled there is no need to update
current->alloc_tag and these manipulations add unnecessary overhead.  Fix
the overhead by skipping these extra updates.

I ran comprehensive testing on Pixel 6 on Big, Medium and Little cores:

                 Overhead before fixes            Overhead after fixes
                 slab alloc      page alloc          slab alloc      page alloc
Big               6.21%           5.32%                3.31%          4.93%
Medium            4.51%           5.05%                3.79%          4.39%
Little            7.62%           1.82%                6.68%          1.02%

This is an allocation microbenchmark doing allocations in a tight loop. 
Not a really realistic scenario and useful only to make performance
comparisons.

Link: https://lkml.kernel.org/r/20241226211639.1357704-1-surenb@google.com
Fixes: b951aaff50 ("mm: enable page allocation tagging")
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Cc: David Wang <00107082@163.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zhenhua Huang <quic_zhenhuah@quicinc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Suren Baghdasaryan 2024-12-26 13:16:38 -08:00 committed by Andrew Morton
parent ade81479c7
commit 0743877931
2 changed files with 10 additions and 3 deletions
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9
include/linux/alloc_tag.h
View File

@ -224,9 +224,14 @@ static inline void alloc_tag_sub(union codetag_ref *ref, size_t bytes) {}
#define alloc_hooks_tag(_tag, _do_alloc) \
({ \
struct alloc_tag * __maybe_unused _old = alloc_tag_save(_tag); \
typeof(_do_alloc) _res = _do_alloc; \
typeof(_do_alloc) _res; \
if (mem_alloc_profiling_enabled()) { \
struct alloc_tag * __maybe_unused _old; \
_old = alloc_tag_save(_tag); \
_res = _do_alloc; \
alloc_tag_restore(_tag, _old); \
} else \
_res = _do_alloc; \
_res; \
})

2
lib/alloc_tag.c
View File

@ -29,6 +29,8 @@ EXPORT_SYMBOL(_shared_alloc_tag);
DEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,
mem_alloc_profiling_key);
EXPORT_SYMBOL(mem_alloc_profiling_key);
DEFINE_STATIC_KEY_FALSE(mem_profiling_compressed);
struct alloc_tag_kernel_section kernel_tags = { NULL, 0 };