Messages in this thread | | | Date | Sat, 13 Mar 2021 23:06:05 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH] perf-stat: introduce bperf, share hardware PMCs with BPF |
| |
On Fri, Mar 12, 2021 at 04:09:53PM +0000, Song Liu wrote: > > > > On Mar 12, 2021, at 7:45 AM, Song Liu <songliubraving@fb.com> wrote: > > > > > > > >> On Mar 12, 2021, at 4:12 AM, Jiri Olsa <jolsa@redhat.com> wrote: > >> > >> On Thu, Mar 11, 2021 at 06:02:57PM -0800, Song Liu wrote: > >>> perf uses performance monitoring counters (PMCs) to monitor system > >>> performance. The PMCs are limited hardware resources. For example, > >>> Intel CPUs have 3x fixed PMCs and 4x programmable PMCs per cpu. > >>> > >>> Modern data center systems use these PMCs in many different ways: > >>> system level monitoring, (maybe nested) container level monitoring, per > >>> process monitoring, profiling (in sample mode), etc. In some cases, > >>> there are more active perf_events than available hardware PMCs. To allow > >>> all perf_events to have a chance to run, it is necessary to do expensive > >>> time multiplexing of events. > >>> > >>> On the other hand, many monitoring tools count the common metrics (cycles, > >>> instructions). It is a waste to have multiple tools create multiple > >>> perf_events of "cycles" and occupy multiple PMCs. > >>> > >>> bperf tries to reduce such wastes by allowing multiple perf_events of > >>> "cycles" or "instructions" (at different scopes) to share PMUs. Instead > >>> of having each perf-stat session to read its own perf_events, bperf uses > >>> BPF programs to read the perf_events and aggregate readings to BPF maps. > >>> Then, the perf-stat session(s) reads the values from these BPF maps. > >>> > >>> Please refer to the comment before the definition of bperf_ops for the > >>> description of bperf architecture. > >>> > >>> bperf is off by default. To enable it, pass --use-bpf option to perf-stat. > >>> bperf uses a BPF hashmap to share information about BPF programs and maps > >>> used by bperf. This map is pinned to bpffs. The default address is > >>> /sys/fs/bpf/bperf_attr_map. The user could change the address with option > >>> --attr-map. > >> > >> nice, I recall the presentation about that and was wondering > >> when this will come up ;-) > > > > The progress is slower than I expected. But I finished some dependencies of > > this in the last year: > > > > 1. BPF_PROG_TEST_RUN for raw_tp event; > > 2. perf-stat -b, which introduced skeleton and bpf_counter; > > 3. BPF task local storage, I didn't use it in this version, but it could, > > help optimize bperf in the future. > > > >> > >>> > >>> --- > >>> Known limitations: > >>> 1. Do not support per cgroup events; > >>> 2. Do not support monitoring of BPF program (perf-stat -b); > >>> 3. Do not support event groups. > >>> > >>> The following commands have been tested: > >>> > >>> perf stat --use-bpf -e cycles -a > >>> perf stat --use-bpf -e cycles -C 1,3,4 > >>> perf stat --use-bpf -e cycles -p 123 > >>> perf stat --use-bpf -e cycles -t 100,101 > >> > >> I assume the output is same as standard perf? > > Btw, please give it a try. :) > > It worked pretty well in my tests. If it doesn't work for some combination > of options, please let me know.
heya, can't compile
CLANG /home/jolsa/linux-perf/tools/perf/util/bpf_skel/.tmp/bperf_follower.bpf.o util/bpf_skel/bperf_follower.bpf.c:8:10: fatal error: 'bperf_u.h' file not found #include "bperf_u.h" ^~~~~~~~~~~
jirka
| |