From 382619c07ff6491b33d54fccff7407336ddcb6d4 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Fri, 26 Apr 2019 09:38:04 +0200 Subject: [PATCH] perf tools: Speed up report for perf compiled with linwunwind When compiled with libunwind, perf does some preparatory work when processing side-band events. This is not needed when report actually don't unwind dwarf callchains, so it's disabled with dwarf_callchain_users bool. However we could move that check to higher level and shield more unwanted code for normal report processing, giving us following speed up on kernel build profile: Before: $ perf record make -j40 ... $ ll ../../perf.data -rw-------. 1 jolsa jolsa 461783932 Apr 26 09:11 perf.data $ perf stat -e cycles:u,instructions:u perf report -i perf.data > out Performance counter stats for 'perf report -i perf.data': 78,669,920,155 cycles:u 99,076,431,951 instructions:u # 1.26 insn per cycle 55.382823668 seconds time elapsed 27.512341000 seconds user 27.712871000 seconds sys After: $ perf stat -e cycles:u,instructions:u perf report -i perf.data > out Performance counter stats for 'perf report -i perf.data': 59,626,798,904 cycles:u 88,583,575,849 instructions:u # 1.49 insn per cycle 21.296935559 seconds time elapsed 20.010191000 seconds user 1.202935000 seconds sys The speed is higher with profile having many side-band events, because these trigger libunwind preparatory code. This does not apply for perf compiled with libdw for dwarf unwind, only for build with libunwind. Signed-off-by: Jiri Olsa Cc: Alexander Shishkin Cc: Namhyung Kim Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20190426073804.17238-1-jolsa@kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/thread.c | 3 ++- tools/perf/util/unwind-libunwind-local.c | 6 ------ tools/perf/util/unwind-libunwind.c | 10 ++++++++++ 3 files changed, 12 insertions(+), 7 deletions(-) diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c index 50678d3..403045a 100644 --- a/tools/perf/util/thread.c +++ b/tools/perf/util/thread.c @@ -15,6 +15,7 @@ #include "map.h" #include "symbol.h" #include "unwind.h" +#include "callchain.h" #include @@ -327,7 +328,7 @@ static int thread__prepare_access(struct thread *thread) { int err = 0; - if (symbol_conf.use_callchain) + if (dwarf_callchain_users) err = __thread__prepare_access(thread); return err; diff --git a/tools/perf/util/unwind-libunwind-local.c b/tools/perf/util/unwind-libunwind-local.c index f3c666a..25e1406 100644 --- a/tools/perf/util/unwind-libunwind-local.c +++ b/tools/perf/util/unwind-libunwind-local.c @@ -617,8 +617,6 @@ static unw_accessors_t accessors = { static int _unwind__prepare_access(struct thread *thread) { - if (!dwarf_callchain_users) - return 0; thread->addr_space = unw_create_addr_space(&accessors, 0); if (!thread->addr_space) { pr_err("unwind: Can't create unwind address space.\n"); @@ -631,15 +629,11 @@ static int _unwind__prepare_access(struct thread *thread) static void _unwind__flush_access(struct thread *thread) { - if (!dwarf_callchain_users) - return; unw_flush_cache(thread->addr_space, 0, 0); } static void _unwind__finish_access(struct thread *thread) { - if (!dwarf_callchain_users) - return; unw_destroy_addr_space(thread->addr_space); } diff --git a/tools/perf/util/unwind-libunwind.c b/tools/perf/util/unwind-libunwind.c index 9778b31..c0811977 100644 --- a/tools/perf/util/unwind-libunwind.c +++ b/tools/perf/util/unwind-libunwind.c @@ -5,6 +5,7 @@ #include "session.h" #include "debug.h" #include "env.h" +#include "callchain.h" struct unwind_libunwind_ops __weak *local_unwind_libunwind_ops; struct unwind_libunwind_ops __weak *x86_32_unwind_libunwind_ops; @@ -24,6 +25,9 @@ int unwind__prepare_access(struct thread *thread, struct map *map, struct unwind_libunwind_ops *ops = local_unwind_libunwind_ops; int err; + if (!dwarf_callchain_users) + return 0; + if (thread->addr_space) { pr_debug("unwind: thread map already set, dso=%s\n", map->dso->name); @@ -65,12 +69,18 @@ out_register: void unwind__flush_access(struct thread *thread) { + if (!dwarf_callchain_users) + return; + if (thread->unwind_libunwind_ops) thread->unwind_libunwind_ops->flush_access(thread); } void unwind__finish_access(struct thread *thread) { + if (!dwarf_callchain_users) + return; + if (thread->unwind_libunwind_ops) thread->unwind_libunwind_ops->finish_access(thread); } -- 2.7.4