ecc68ee216
It seems that perf stat -b <prog id> doesn't produce any results:
$ perf stat -e cycles -b 4 -I 10000 -vvv
Control descriptor is not initialized
cycles: 0 0 0
time counts unit events
10.007641640 <not supported> cycles
Looks like this happens because fentry/fexit progs are getting loaded, but the
corresponding perf event is not enabled and not added into the events bpf map.
I think there is some mixing up between two type of bpf support, one for bperf
and one for bpf_profiler. Both are identified via evsel__is_bpf, based on which
perf events are enabled, but for the latter (bpf_profiler) a perf event is
required. Using evsel__is_bperf to check only bperf produces expected results:
$ perf stat -e cycles -b 4 -I 10000 -vvv
Control descriptor is not initialized
------------------------------------------------------------
perf_event_attr:
size 136
sample_type IDENTIFIER
read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
disabled 1
exclude_guest 1
------------------------------------------------------------
sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8 = 3
------------------------------------------------------------
[...perf_event_attr for other CPUs...]
------------------------------------------------------------
cycles: 309426 169009 169009
time counts unit events
10.010091271 309426 cycles
The final numbers correspond (at least in the level of magnitude) to the
same metric obtained via bpftool.
Fixes: 112cb56164bc2108 ("perf stat: Introduce config stat.bpf-counter-events")
Reviewed-by: Song Liu <song@kernel.org>
Signed-off-by: Dmitrii Dolgov <9erthalion6@gmail.com>
Tested-by: Song Liu <song@kernel.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230412182316.11628-1-9erthalion6@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.