bdacfaf26d
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 |
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| callchain.c | ||
| core.c | ||
| hw_breakpoint.c | ||
| internal.h | ||
| Makefile | ||
| ring_buffer.c | ||
| uprobes.c | ||