Re: [PATCH v7] perf tools: add support for libpfm4

[Jiri Olsa]

On Mon, Apr 06, 2020 at 11:40:18PM -0700, Ian Rogers wrote:
> From: Stephane Eranian <eranian@xxxxxxxxxx>
> 
> This patch links perf with the libpfm4 library if it is available and
> NO_LIBPFM4 isn't passed to the build. The libpfm4 library contains hardware
> event tables for all processors supported by perf_events. It is a helper
> library that helps convert from a symbolic event name to the event
> encoding required by the underlying kernel interface. This
> library is open-source and available from: http://perfmon2.sf.net.
> 
> With this patch, it is possible to specify full hardware events
> by name. Hardware filters are also supported. Events must be
> specified via the --pfm-events and not -e option. Both options
> are active at the same time and it is possible to mix and match:
> 
> $ perf stat --pfm-events inst_retired:any_p:c=1:i -e cycles ....
> 
> v7 rebases and adds fallback code for libpfm4 events.
>    The fallback code is to force user only priv level in case the
>    perf_event_open() syscall failed for permissions reason.
>    the fallback forces a user privilege level restriction on the event string,
>    so depending on the syntax either u or :u is needed.
> 
>    But libpfm4 can use a : or . as the separator, so simply searching
>    for ':' vs. '/' is not good enough to determine the syntax needed.
>    Therefore, this patch introduces a new evsel boolean field to mark events
>    coming from  libpfm4. The field is then used to adjust the fallback string.

heya,
I made bunch of comments for v5, not sure you saw them:
  https://lore.kernel.org/lkml/20200323235846.104937-1-irogers@xxxxxxxxxx/

jirka

> v6 is a rebase.
> v5 is a rebase.
> v4 is a rebase on git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git
>    branch perf/core and re-adds the tools/build/feature/test-libpfm4.c
>    missed in v3.
> v3 is against acme/perf/core and removes a diagnostic warning.
> v2 of this patch makes the --pfm-events man page documentation
> conditional on libpfm4 behing configured. It tidies some of the
> documentation and adds the feature test missed in the v1 patch.
> 

SNIP