Messages in this thread | | | Date | Fri, 12 Mar 2021 13:12:48 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH] perf-stat: introduce bperf, share hardware PMCs with BPF |
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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 ;-)
> > --- > 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?
jirka
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