Messages in this thread | | | Date | Fri, 3 Apr 2020 13:01:37 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCH v2 0/5] Benchmark and improve event synthesis performance |
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On Thu, Apr 02, 2020 at 08:43:52AM -0700, Ian Rogers wrote: > Event synthesis is performance critical in common tasks using perf. For > example, when perf record starts in system wide mode the /proc file > system is scanned with events synthesized for each process and all > executable mmaps. With large machines and lots of processes, we have seen > O(seconds) of wall clock time while synthesis is occurring. > > This patch set adds a benchmark for synthesis performance in a new > benchmark collection called 'internals'. The benchmark uses the > machine__synthesize_threads function, single threaded on the perf process > with a 'tool' that just drops the events, to measure how long synthesis > takes. > > By profiling this benchmark 2 performance bottlenecks were identified, > hugetlbfs_mountpoint and stdio. The impact of theses changes are: > > Before: > Average synthesis took: 167.616800 usec > Average data synthesis took: 208.655600 usec > > After hugetlbfs_mountpoint scalability fix: > Average synthesis took: 120.195100 usec > Average data synthesis took: 156.582300 usec > > After removal of stdio in /proc/pid/maps code: > Average synthesis took: 67.189100 usec > Average data synthesis took: 102.451600 usec > > Time was measured on an Intel Xeon 6154 compiling with Debian gcc 9.2.1. > > v2 of this patch set adds the new benchmark to the perf-bench man page > and addresses review comments from Jiri Olsa, thanks!
Acked-by: Jiri Olsa <jolsa@redhat.com>
thanks, jirka
> > Two patches in the set were sent to LKML previously but are included > here for context around the benchmark performance impact: > https://lore.kernel.org/lkml/20200327172914.28603-1-irogers@google.com/T/#u > https://lore.kernel.org/lkml/20200328014221.168130-1-irogers@google.com/T/#u > > A future area of improvement could be to add the perf top > num-thread-synthesize option more widely to other perf commands, and > also to benchmark its effectiveness. > > Ian Rogers (4): > perf bench: add event synthesis benchmark > perf synthetic-events: save 4kb from 2 stack frames > tools api: add a lightweight buffered reading api > perf synthetic events: Remove use of sscanf from /proc reading > > Stephane Eranian (1): > tools api fs: make xxx__mountpoint() more scalable > > tools/lib/api/fs/fs.c | 17 +++ > tools/lib/api/fs/fs.h | 12 ++ > tools/lib/api/io.h | 107 ++++++++++++++ > tools/perf/Documentation/perf-bench.txt | 8 ++ > tools/perf/bench/Build | 2 +- > tools/perf/bench/bench.h | 2 +- > tools/perf/bench/synthesize.c | 101 ++++++++++++++ > tools/perf/builtin-bench.c | 6 + > tools/perf/util/synthetic-events.c | 177 +++++++++++++++--------- > 9 files changed, 367 insertions(+), 65 deletions(-) > create mode 100644 tools/lib/api/io.h > create mode 100644 tools/perf/bench/synthesize.c > > -- > 2.26.0.rc2.310.g2932bb562d-goog >
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