lkml.org 
[lkml]   [2022]   [Feb]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH bpf-next v2] bpf: Cache the last valid build_id.
On Wed, Feb 23, 2022 at 4:11 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Wed, Feb 23, 2022 at 4:05 PM Hao Luo <haoluo@google.com> wrote:
> >
> > For binaries that are statically linked, consecutive stack frames are
> > likely to be in the same VMA and therefore have the same build id.
> > As an optimization for this case, we can cache the previous frame's
> > VMA, if the new frame has the same VMA as the previous one, reuse the
> > previous one's build id. We are holding the MM locks as reader across
> > the entire loop, so we don't need to worry about VMA going away.
> >
> > Tested through "stacktrace_build_id" and "stacktrace_build_id_nmi" in
> > test_progs.
> >
> > Suggested-by: Greg Thelen <gthelen@google.com>
> > Signed-off-by: Hao Luo <haoluo@google.com>
> > ---
>
> LGTM. Can you share performance numbers before and after?
>
> Acked-by: Andrii Nakryiko <andrii@kernel.org>
>

Thanks Andrii.

On a real-world workload, we observed that 66% of cpu cycles in
__bpf_get_stackid() were spent on build_id_parse() and find_vma().
This was before.

We haven't evaluated the performance with this patch yet. This
optimization seems straightforward, so we plan to upstream it first
and then retest.

\
 
 \ /
  Last update: 2022-02-24 01:36    [W:0.044 / U:0.432 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site