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From:   Hao Luo <haoluo@google.com>
Date:   Wed, 23 Feb 2022 15:40:16 -0800
Message-ID: <CA+khW7hKQcJ30om+XzrCa-Aj=r9eHAHETS=7qtVW6+t480w2uQ@mail.gmail.com>
Subject: Re: [PATCH bpf-next] bpf: Cache the last valid build_id.
To:     Greg Thelen <gthelen@google.com>
Cc:     Andrii Nakryiko <andrii.nakryiko@gmail.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Song Liu <songliubraving@fb.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Blake Jones <blakejones@google.com>, bpf <bpf@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>
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On Wed, Feb 23, 2022 at 3:16 PM Greg Thelen <gthelen@google.com> wrote:
>
> Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>
> >
> > as a further optimization, shouldn't we first check if ips[i] is
> > within prev_vma and avoid rbtree walk altogether? Would this work:
> >
> > if (prev_vma && range_in_vma(prev_vma, ips[i])) {
> >    /* reuse build_id */
> > }
> > vma = find_vma(current->mm, ips[i]);
> >
> >
> > ?
>
> Yes, that's a nice addition. Good idea.

Yes, great point!

I noticed range_in_vma() already has a check on the null-ness of
prev_vma. I am going to send a v2.