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

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Message-ID: <7ec772fb-2108-5945-a308-4bb46fcf0090@linux.dev>
Date:   Mon, 9 Jan 2023 13:22:46 -0800
From:   Martin KaFai Lau <martin.lau@...ux.dev>
To:     Namhyung Kim <namhyung@...nel.org>
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 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.