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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 <jolsa@kernel.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20190426073804.17238-1-jolsa@kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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3 changed files with 12 additions and 7 deletions
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@ -15,6 +15,7 @@
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#include "map.h"
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#include "symbol.h"
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#include "unwind.h"
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#include "callchain.h"
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#include <api/fs/fs.h>
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@ -327,7 +328,7 @@ static int thread__prepare_access(struct thread *thread)
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{
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int err = 0;
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if (symbol_conf.use_callchain)
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if (dwarf_callchain_users)
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err = __thread__prepare_access(thread);
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return err;
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@ -617,8 +617,6 @@ static unw_accessors_t accessors = {
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static int _unwind__prepare_access(struct thread *thread)
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{
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if (!dwarf_callchain_users)
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return 0;
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thread->addr_space = unw_create_addr_space(&accessors, 0);
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if (!thread->addr_space) {
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pr_err("unwind: Can't create unwind address space.\n");
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@ -631,15 +629,11 @@ static int _unwind__prepare_access(struct thread *thread)
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static void _unwind__flush_access(struct thread *thread)
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{
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if (!dwarf_callchain_users)
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return;
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unw_flush_cache(thread->addr_space, 0, 0);
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}
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static void _unwind__finish_access(struct thread *thread)
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{
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if (!dwarf_callchain_users)
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return;
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unw_destroy_addr_space(thread->addr_space);
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}
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@ -5,6 +5,7 @@
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#include "session.h"
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#include "debug.h"
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#include "env.h"
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#include "callchain.h"
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struct unwind_libunwind_ops __weak *local_unwind_libunwind_ops;
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struct unwind_libunwind_ops __weak *x86_32_unwind_libunwind_ops;
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@ -24,6 +25,9 @@ int unwind__prepare_access(struct thread *thread, struct map *map,
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struct unwind_libunwind_ops *ops = local_unwind_libunwind_ops;
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int err;
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if (!dwarf_callchain_users)
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return 0;
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if (thread->addr_space) {
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pr_debug("unwind: thread map already set, dso=%s\n",
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map->dso->name);
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@ -65,12 +69,18 @@ int unwind__prepare_access(struct thread *thread, struct map *map,
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void unwind__flush_access(struct thread *thread)
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{
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if (!dwarf_callchain_users)
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return;
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if (thread->unwind_libunwind_ops)
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thread->unwind_libunwind_ops->flush_access(thread);
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}
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void unwind__finish_access(struct thread *thread)
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{
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if (!dwarf_callchain_users)
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return;
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if (thread->unwind_libunwind_ops)
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thread->unwind_libunwind_ops->finish_access(thread);
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}
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