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Date:   Mon, 9 Jan 2023 13:22:46 -0800
MIME-Version: 1.0
Subject: Re: [PATCH] perf lock contention: Do not use BPF task local storage
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To:     Namhyung Kim <namhyung@kernel.org>
Cc:     Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Ian Rogers <irogers@google.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        linux-perf-users@vger.kernel.org, Song Liu <song@kernel.org>,
        bpf@vger.kernel.org, Blake Jones <blakejones@google.com>,
        Chris Li <chriscli@google.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@kernel.org>
References: <20221118190109.1512674-1-namhyung@kernel.org>
 <dea8c3c5-0739-58c1-9a88-b989878a9b8f@linux.dev>
 <CAM9d7cjk_7-ALzW1kT961TRLpO9Wt8gNX7+rH4ay4N92g1TYkg@mail.gmail.com>
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From:   Martin KaFai Lau <martin.lau@linux.dev>
In-Reply-To: <CAM9d7cjk_7-ALzW1kT961TRLpO9Wt8gNX7+rH4ay4N92g1TYkg@mail.gmail.com>
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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@linux.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.