linux-kernel - Re: [PATCH] perf lock contention: Do not use BPF task local storage

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Message-ID: <CAM9d7cgb=NjRLt9i00RaOmseLytOF4WMRAXyFiH3LnuVnGHCZQ@mail.gmail.com>
Date:   Mon, 9 Jan 2023 14:25:44 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Martin KaFai Lau <martin.lau@...ux.dev>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, Song Liu <song@...nel.org>,
        bpf@...r.kernel.org, Blake Jones <blakejones@...gle.com>,
        Chris Li <chriscli@...gle.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>
Subject: Re: [PATCH] perf lock contention: Do not use BPF task local storage

On Mon, Jan 9, 2023 at 1:23 PM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>
> On 1/9/23 12:56 PM, Namhyung Kim wrote:
> > Hello,
> >
> > On Mon, Nov 21, 2022 at 9:33 AM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
> >>
> >> On 11/18/22 11:01 AM, Namhyung Kim wrote:
> >>> We could fix the task local storage to use the safe BPF allocator,
> >>> but it takes time so let's change this until it happens actually.
> >>
> >> I also got another report on the kfree_rcu path.  I am also looking into this
> >> direction on using the BPF allocator.
> >
> > Any progress on this?  Are there any concerns about the change?
>
> Yep, I am working on it. It is not a direct replacement from kzalloc to
> bpf_mem_cache_alloc. eg. Some changes in the bpf mem allocator is needed to
> ensure the free list cannot be reused before the rcu grace period. There is a
> similar RFC patchset going into this direction that I am trying with.

I see.  Thanks for the update!

Namhyung