Hi Mikołaj, On Sun, Jun 23, 2024 at 02:02:36AM GMT, Mikołaj Kołek wrote: > After calling perf_event_open() with cpus == -1 and the inherit bit, > using mmap on the perf file descriptor to create a ring-buffer fails > with EINVAL. This behavior wasn't previously documented in the man > page and is caused by the following lines in the perf_mmap function in > kernel/events/core.c: > /* > * Don't allow mmap() of inherited per-task counters. This would > * create a performance issue due to all children writing to the > * same rb. > */ > if (event->cpu == -1 && event->attr.inherit) > return -EINVAL; Thanks for the detailed commit message! > Signed-off-by: Mikołaj Kołek <kolek.mikolaj@xxxxxxxxx> > --- > man/man2/perf_event_open.2 | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/man/man2/perf_event_open.2 b/man/man2/perf_event_open.2 > index 2f345ff5b..15a5972d0 100644 > --- a/man/man2/perf_event_open.2 > +++ b/man/man2/perf_event_open.2 > @@ -1025,6 +1025,10 @@ .SS Arguments > .I read_format Applying: perf_event_open.2: document combining inherit and cpus = -1 preventing the use of mmap error: corrupt patch at line 10 Patch failed at 0001 perf_event_open.2: document combining inherit and cpus = -1 preventing the use of mmap hint: Use 'git am --show-current-patch=diff' to see the failed patch hint: When you have resolved this problem, run "git am --continue". hint: If you prefer to skip this patch, run "git am --skip" instead. hint: To restore the original branch and stop patching, run "git am --abort". hint: Disable this message with "git config advice.mergeConflict false" Press any key to continue... The patch seems to be corrupt. Context lines should begin with a space. Can you fix that on your end? Otherwise, I'll manually apply the patch. > values, such as > .BR PERF_FORMAT_GROUP . > +Additionally, using it together with > +.BR "cpu == -1" Please make this .I cpu == \-1 > +prevents the creation of the mmap ring-buffer used for > +logging asynchronous events in sampled mode. > .TP > .I pinned > The > -- > 2.45.2 Have a lovely day! Alex > -- <https://www.alejandro-colomar.es/>
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