[Bug 1999551] Re: glibc: backport AArch64 memcmp improvements

Tue Jun 6 19:54:18 UTC 2023

Hello Simon, or anyone else affected,

Accepted glibc into jammy-proposed. The package will build now and be
available at https://launchpad.net/ubuntu/+source/glibc/2.35-0ubuntu3.2
in a few hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
jammy to verification-done-jammy. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-jammy. In either case, without details of your testing we will
not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Description changed:

  [impact]

  There have been relatively recent improvements to the memcmp and memcpy
- routines for server-grage AArch64 implementation, in particular AWS's
+ routines for server-grade AArch64 implementation, in particular AWS's
  Graviton3.

  We'd like to backport those improvements to Jammy and Focal when
  appropriate, under the HWE umbrella.

  The relevant patches are

  https://sourceware.org/git/?p=glibc.git;a=commit;h=9f298bfe1f183804bb54b54ff9071afc0494906c (Jammy & Focal)
  https://sourceware.org/git/?p=glibc.git;a=commit;h=b51eb35c572b015641f03e3682c303f7631279b7 (Focal only, already present in Jammy)

  In addition, to be able to actually test the changes and its impact on
  all architectures, we'll need the following fix:

  https://sourceware.org/git/?p=glibc.git;a=commit;h=311a7e0256975275d97077f1af338bc9caf0c837

  [test case]

  Since those are optimization patches, we'll be relying on the
  autopkgtests triggered by the upload for regression detection.

  However, we'll also benchmark the optimizations on Graviton AWS
  instances as well as various Raspberry Pi models to ensure there is no
  severe performance regression on those platforms.

  To do the performance test, first install the libc from this PPA:

  https://launchpad.net/~schopin/+archive/ubuntu/glibc-benchmark

  that is the current Jammy glibc with the extra fix for benchmarking.

  Then, untar the attached archive bench-timing.tar.xz on the target
  platform, and follow the instructions from the README.

  [Regression potential]

  This could potentially impact performance on other, non-server-grade
  arm64 platforms such as RPi. Furthermore, there could be unforeseen
  issues with the newly optimized routine in edge cases (a recent amd64
  optimization had issues on page boundaries, for instance).

** Changed in: glibc (Ubuntu Jammy)
       Status: In Progress => Fix Committed

** Tags added: verification-needed verification-needed-jammy

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https://bugs.launchpad.net/bugs/1999551

Title:
  glibc: backport AArch64 memcmp improvements

Status in glibc package in Ubuntu:
  Fix Released
Status in glibc source package in Focal:
  In Progress
Status in glibc source package in Jammy:
  Fix Committed
Status in glibc source package in Kinetic:
  Fix Released

Bug description:
  [impact]

  There have been relatively recent improvements to the memcmp and
  memcpy routines for server-grade AArch64 implementation, in particular
  AWS's Graviton3.