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From: "gprocida at google dot com" <sourceware-bugzilla@sourceware.org>
To: libabigail@sourceware.org
Subject: [Bug default/29464] New: abidw performance regression on vmlinux
Date: Tue, 09 Aug 2022 17:57:50 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D29464

            Bug ID: 29464
           Summary: abidw performance regression on vmlinux
           Product: libabigail
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: default
          Assignee: dodji at redhat dot com
          Reporter: gprocida at google dot com
                CC: libabigail at sourceware dot org
  Target Milestone: ---

Hi Dodji.

I've been testing changes since our last upstream merge and have found a
performance regression.

A typical standalone "abidw vmlinux" normally takes around 20s on an AOSP
kernel. Following the merge, run times are around 1.5h. So that's around 270
times slower.

Using almost vanilla upstream libabigail (I had to disable one ELF symbol
assertion for unrelated reasons), I was able to bisect the regression to:

7ecef6361799326b99129a479b43b138f0b237ae "Canonicalize DIEs w/o assuming OD=
R &
handle typedefs transparently"

This commit does a few things, but most significantly removes an optimisati=
on
that assumed the ODR.

The change in behaviour was consistent across 6 different test kernels and a
couple of other kernels I had lying around from different test cases. Howev=
er,
in one case, abidw ran quickly as normal.

It's very likely that one of the previous kernels you've had from me will
trigger the problem. I will also see if I can find "off the shelf" binary t=
hat
you can debug with.

Regards,
Giuliano.

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