Hi, On 05.09.2018 14:28, Jiri Olsa wrote: > On Wed, Sep 05, 2018 at 10:16:42AM +0300, Alexey Budankov wrote: >> >> Currently in record mode the tool implements trace writing serially. >> The algorithm loops over mapped per-cpu data buffers and stores >> ready data chunks into a trace file using write() system call. >> >> At some circumstances the kernel may lack free space in a buffer >> because the other buffer's half is not yet written to disk due to >> some other buffer's data writing by the tool at the moment. >> >> Thus serial trace writing implementation may cause the kernel >> to loose profiling data and that is what observed when profiling >> highly parallel CPU bound workloads on machines with big number >> of cores. >> >> Experiment with profiling matrix multiplication code executing 128 >> threads on Intel Xeon Phi (KNM) with 272 cores, like below, >> demonstrates data loss metrics value of 98%: >> >> /usr/bin/time perf record -o /tmp/perf-ser.data -a -N -B -T -R -g \ >> --call-graph dwarf,1024 --user-regs=IP,SP,BP \ >> --switch-events -e >> cycles,instructions,ref-cycles,software/period=1,name=cs,config=0x3/Duk -- \ >> matrix.gcc >> >> Data loss metrics is the ratio lost_time/elapsed_time where >> lost_time is the sum of time intervals containing PERF_RECORD_LOST >> records and elapsed_time is the elapsed application run time >> under profiling. >> >> Applying asynchronous trace streaming thru Posix AIO API >> (http://man7.org/linux/man-pages/man7/aio.7.html) >> lowers data loss metrics value providing 2x improvement - >> lowering 98% loss to almost 0%. >> >> --- >> Alexey Budankov (2): >> perf util: map data buffer for preserving collected data >> perf record: enable asynchronous trace writing >> >> tools/perf/builtin-record.c | 197 >> +++++++++++++++++++++++++++++++++++++++++++- >> tools/perf/perf.h | 1 + >> tools/perf/util/evlist.c | 7 +- >> tools/perf/util/evlist.h | 3 +- >> tools/perf/util/mmap.c | 110 +++++++++++++++++++++---- >> tools/perf/util/mmap.h | 10 ++- >> 6 files changed, 302 insertions(+), 26 deletions(-) >> >> --- >> Changes in v7: >> - implemented handling record.aio setting from perfconfig file > > can't apply this version on Arnaldo's perf/core...
my git remote -v origin git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip (fetch) origin git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip (push) branch is perf/core, according to MAINTAINERS content. What is Arnaldo's perf/core? This one? git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux and branch is perf/core? > > [jolsa@krava linux-perf]$ git am /tmp/ab/ > Applying: perf util: map data buffer for preserving collected data > error: patch failed: tools/perf/util/mmap.c:166 > error: tools/perf/util/mmap.c: patch does not apply > > thanks, > jirka >
