perf bench breakpoint: Fix build on 32-bit arches

2022-05-17T00:23:09Z

Cast pointers to unsigned long instead of to uint64_t to avoid this problem on 32-bit arches: 31 6.89 debian:experimental-x-mips : FAIL gcc version 11.2.0 (Debian 11.2.0-18) bench/breakpoint.c: In function 'breakpoint_setup': bench/breakpoint.c:56:24: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast] 56 | attr.bp_addr = (uint64_t)addr; | ^ cc1: all warnings being treated as errors make[3]: *** [/git/perf-5.18.0-rc7/tools/build/Makefile.build:139: bench] Error 2 Fixes: 68a6772f11dbb1ed ("perf bench: Add breakpoint benchmarks") Cc: Adrian Hunter Cc: Alexander Shishkin Cc: Dmitriy Vyukov Cc: Ian Rogers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Marco Elver Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Link: http://lore.kernel.org/lkml/YoLq1nHx1doi+VWl@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf bench: Add breakpoint benchmarks

2022-05-13T14:00:38Z

Add 2 benchmarks: 1. Performance of thread creation/exiting in presence of breakpoints. 2. Performance of breakpoint modification in presence of threads. The benchmarks capture use cases that we are interested in: using inheritable breakpoints in large highly-threaded applications. The benchmarks show significant slowdown imposed by breakpoints (even when they don't fire). Testing on Intel 8173M with 112 HW threads show: perf bench --repeat=56 breakpoint thread --breakpoints=0 --parallelism=56 --threads=20 78.675000 usecs/op perf bench --repeat=56 breakpoint thread --breakpoints=4 --parallelism=56 --threads=20 12967.135714 usecs/op That's 165x slowdown due to presence of the breakpoints. perf bench --repeat=20000 breakpoint enable --passive=0 --active=0 1.433250 usecs/op perf bench --repeat=20000 breakpoint enable --passive=224 --active=0 585.318400 usecs/op perf bench --repeat=20000 breakpoint enable --passive=0 --active=111 635.953000 usecs/op That's 408x and 444x slowdown due to presence of threads. Profiles show some overhead in toggle_bp_slot, but also very high contention: 90.83% breakpoint-thre [kernel.kallsyms] [k] osq_lock 4.69% breakpoint-thre [kernel.kallsyms] [k] mutex_spin_on_owner 2.06% breakpoint-thre [kernel.kallsyms] [k] __reserve_bp_slot 2.04% breakpoint-thre [kernel.kallsyms] [k] toggle_bp_slot 79.01% breakpoint-enab [kernel.kallsyms] [k] smp_call_function_single 9.94% breakpoint-enab [kernel.kallsyms] [k] llist_add_batch 5.70% breakpoint-enab [kernel.kallsyms] [k] _raw_spin_lock_irq 1.84% breakpoint-enab [kernel.kallsyms] [k] event_function_call 1.12% breakpoint-enab [kernel.kallsyms] [k] send_call_function_single_ipi 0.37% breakpoint-enab [kernel.kallsyms] [k] generic_exec_single 0.24% breakpoint-enab [kernel.kallsyms] [k] __perf_event_disable 0.20% breakpoint-enab [kernel.kallsyms] [k] _perf_event_enable 0.18% breakpoint-enab [kernel.kallsyms] [k] toggle_bp_slot Committer notes: Fixup struct init for older compilers: 3 32.90 alpine:3.5 : FAIL clang version 3.8.1 (tags/RELEASE_381/final) bench/breakpoint.c:49:34: error: missing field 'size' initializer [-Werror,-Wmissing-field-initializers] struct perf_event_attr attr = {0}; ^ 1 error generated. 7 37.31 alpine:3.9 : FAIL gcc version 8.3.0 (Alpine 8.3.0) bench/breakpoint.c:49:34: error: missing field 'size' initializer [-Werror,-Wmissing-field-initializers] struct perf_event_attr attr = {0}; ^ 1 error generated. Signed-off-by: Dmitriy Vyukov Tested-by: Arnaldo Carvalho de Melo Acked-by: Ian Rogers Cc: Alexander Shishkin Cc: Ingo Molnar Cc: Jiri Olsa Cc: Marco Elver Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20220505155745.1690906-1-dvyukov@google.com Signed-off-by: Arnaldo Carvalho de Melo

linux-dev/tools/perf/bench/breakpoint.c, branch linus/master

perf bench breakpoint: Fix build on 32-bit arches

perf bench: Add breakpoint benchmarks