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| author |   Namhyung Kim <namhyung@google.com> | 2021-03-11 20:54:12 +0900 |
|---|---|---|
| committer |   Peter Zijlstra <peterz@infradead.org> | 2021-03-16 21:44:42 +0100 |
| commit | bdacfaf26da166dd56c62f23f27a4b3e71f2d89e (patch) | |
| tree | ec997eec7ea48b7875e1de7902a72ad80e8d5196 /kernel/events | |
| parent | perf core: Allocate perf_buffer in the target node memory (diff) | |
| download | linux-dev-bdacfaf26da166dd56c62f23f27a4b3e71f2d89e.tar.xz linux-dev-bdacfaf26da166dd56c62f23f27a4b3e71f2d89e.zip | |
perf core: Add a kmem_cache for struct perf_event
The kernel can allocate a lot of struct perf_event when profiling. For
example, 256 cpu x 8 events x 20 cgroups = 40K instances of the struct
would be allocated on a large system.
The size of struct perf_event in my setup is 1152 byte. As it's
allocated by kmalloc, the actual allocation size would be rounded up
to 2K.
Then there's 896 byte (~43%) of waste per instance resulting in total
~35MB with 40K instances. We can create a dedicated kmem_cache to
avoid such a big unnecessary memory consumption.
With this change, I can see below (note this machine has 112 cpus).
# grep perf_event /proc/slabinfo
perf_event 224 784 1152 7 2 : tunables 24 12 8 : slabdata 112 112 0
The sixth column is pages-per-slab which is 2, and the fifth column is
obj-per-slab which is 7. Thus actually it can use 1152 x 7 = 8064
byte in the 8K, and wasted memory is (8192 - 8064) / 7 = ~18 byte per
instance.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210311115413.444407-1-namhyung@kernel.org
Diffstat (limited to 'kernel/events')
| -rw-r--r-- | kernel/events/core.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index 03db40f6cba9..f526ddb50d5e 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -405,6 +405,7 @@ static LIST_HEAD(pmus); static DEFINE_MUTEX(pmus_lock); static struct srcu_struct pmus_srcu; static cpumask_var_t perf_online_mask; +static struct kmem_cache *perf_event_cache; /* * perf event paranoia level: @@ -4611,7 +4612,7 @@ static void free_event_rcu(struct rcu_head *head) if (event->ns) put_pid_ns(event->ns); perf_event_free_filter(event); - kfree(event); + kmem_cache_free(perf_event_cache, event); } static void ring_buffer_attach(struct perf_event *event, @@ -11293,7 +11294,7 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu, return ERR_PTR(-EINVAL); } - event = kzalloc(sizeof(*event), GFP_KERNEL); + event = kmem_cache_zalloc(perf_event_cache, GFP_KERNEL); if (!event) return ERR_PTR(-ENOMEM); @@ -11497,7 +11498,7 @@ err_ns: put_pid_ns(event->ns); if (event->hw.target) put_task_struct(event->hw.target); - kfree(event); + kmem_cache_free(perf_event_cache, event); return ERR_PTR(err); } @@ -13130,6 +13131,8 @@ void __init perf_event_init(void) ret = init_hw_breakpoint(); WARN(ret, "hw_breakpoint initialization failed with: %d", ret); + perf_event_cache = KMEM_CACHE(perf_event, SLAB_PANIC); + /* * Build time assertion that we keep the data_head at the intended * location. IOW, validation we got the __reserved[] size right. |