diff options
| author | Andrii Nakryiko <andrii@kernel.org> | 2024-04-24 14:52:14 -0700 |
|---|---|---|
| committer | Masami Hiramatsu (Google) <mhiramat@kernel.org> | 2024-05-01 23:18:48 +0900 |
| commit | 78d0b16127daa26d016c215a089ae330878291f7 (patch) | |
| tree | d9fef1a56441ea32fd2e5cae6d6fb39b71be0350 /include/linux/objpool.h | |
| parent | a3b00f10da808bd4a354f890b551cba471082d0e (diff) | |
objpool: cache nr_possible_cpus() and avoid caching nr_cpu_ids
Profiling shows that calling nr_possible_cpus() in objpool_pop() takes
a noticeable amount of CPU (when profiled on 80-core machine), as we
need to recalculate number of set bits in a CPU bit mask. This number
can't change, so there is no point in paying the price for recalculating
it. As such, cache this value in struct objpool_head and use it in
objpool_pop().
On the other hand, cached pool->nr_cpus isn't necessary, as it's not
used in hot path and is also a pretty trivial value to retrieve. So drop
pool->nr_cpus in favor of using nr_cpu_ids everywhere. This way the size
of struct objpool_head remains the same, which is a nice bonus.
Same BPF selftests benchmarks were used to evaluate the effect. Using
changes in previous patch (inlining of objpool_pop/objpool_push) as
baseline, here are the differences:
BASELINE
========
kretprobe : 9.937 ± 0.174M/s
kretprobe-multi: 10.440 ± 0.108M/s
AFTER
=====
kretprobe : 10.106 ± 0.120M/s (+1.7%)
kretprobe-multi: 10.515 ± 0.180M/s (+0.7%)
Link: https://lore.kernel.org/all/20240424215214.3956041-3-andrii@kernel.org/
Cc: Matt (Qiang) Wu <wuqiang.matt@bytedance.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Diffstat (limited to 'include/linux/objpool.h')
| -rw-r--r-- | include/linux/objpool.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/include/linux/objpool.h b/include/linux/objpool.h index d8b1f7b91128..cb1758eaa2d3 100644 --- a/include/linux/objpool.h +++ b/include/linux/objpool.h @@ -73,7 +73,7 @@ typedef int (*objpool_fini_cb)(struct objpool_head *head, void *context); * struct objpool_head - object pooling metadata * @obj_size: object size, aligned to sizeof(void *) * @nr_objs: total objs (to be pre-allocated with objpool) - * @nr_cpus: local copy of nr_cpu_ids + * @nr_possible_cpus: cached value of num_possible_cpus() * @capacity: max objs can be managed by one objpool_slot * @gfp: gfp flags for kmalloc & vmalloc * @ref: refcount of objpool @@ -85,7 +85,7 @@ typedef int (*objpool_fini_cb)(struct objpool_head *head, void *context); struct objpool_head { int obj_size; int nr_objs; - int nr_cpus; + int nr_possible_cpus; int capacity; gfp_t gfp; refcount_t ref; @@ -176,7 +176,7 @@ static inline void *objpool_pop(struct objpool_head *pool) raw_local_irq_save(flags); cpu = raw_smp_processor_id(); - for (i = 0; i < num_possible_cpus(); i++) { + for (i = 0; i < pool->nr_possible_cpus; i++) { obj = __objpool_try_get_slot(pool, cpu); if (obj) break; |