linux-kernel - Re: [RFC 00/48] perf tools: Introduce data type profiling (v1)

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Date:   Thu, 12 Oct 2023 13:45:04 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Stephane Eranian <eranian@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        linux-toolchains@...r.kernel.org,
        linux-trace-devel@...r.kernel.org,
        Ben Woodard <woodard@...hat.com>,
        Joe Mario <jmario@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        David Blaikie <blaikie@...gle.com>,
        Xu Liu <xliuprof@...gle.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Ravi Bangoria <ravi.bangoria@....com>
Subject: Re: [RFC 00/48] perf tools: Introduce data type profiling (v1)

On Thu, Oct 12, 2023 at 11:33 AM Ingo Molnar <mingo@...nel.org> wrote:
>
>
> * Namhyung Kim <namhyung@...nel.org> wrote:
>
> > > Could we perhaps add an IP filter to perf events to get this built-in?
> > > Perhaps attr->exclude_user would achieve something similar?
> >
> > Unfortunately IBS doesn't support privilege filters IIUC.  Maybe
> > we could add a general filtering logic in the NMI handler but I'm
> > afraid it can complicate the code and maybe slow it down a bit.
> > Probably it's ok to have only a simple privilege filter by IP range.
>
> It will still be so much faster than moving it through the BPF machinery,
> and bonus points if we merge this into the existing privilege-domain
> filtering ABI, so no magic 0x800000000000 constants are needed.
>
> 'Overhead' to other usecases shouldn't be much more than a single branch
> somewhere.

Ok, maybe overhead is not a concern.  But users need to pass the
filter expression to the kernel.

Thanks,
Namhyung