** Tags removed: rls-jj-incoming
** Tags added: foundations-todo
** Changed in: glibc (Ubuntu Jammy)
Assignee: Mauricio Faria de Oliveira (mfo) => Simon Chopin (schopin)
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** Attachment added: "test-glibc-malloc.c"
https://bugs.launchpad.net/ubuntu/+source/glibc/+bug/2089789/+attachment/5841534/+files/test-glibc-malloc.c
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** Description changed:
[Impact]
* Jammy has a malloc() performance degradation
if CPU affinity masks are used (not default).
* The maximum number of arenas for malloc() is
calculated based on the number of processors.
However, glibc 2.34 changed that to be based
Coordinated this SRU with Simon Chopin in Foundations,
who handles most glibc uploads; this will be discussed
and planned for the next round of bug-fixes/glibc SRU.
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Debdiff used for the PPA builds (successful in all architectures).
** Patch added: "lp2089789-glibc-jammy.debdiff"
https://bugs.launchpad.net/ubuntu/+source/glibc/+bug/2089789/+attachment/5840918/+files/lp2089789-glibc-jammy.debdiff
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** Tags added: rls-jj-incoming
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https://bugs.launchpad.net/bugs/2089789
Title:
malloc performance degradation with CPU affinity masks
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Build-testing in all supported architectures in a PPA with only the -security
pocket enabled.
https://launchpad.net/~mfo/+archive/ubuntu/lp2089789
** Description changed:
[Impact]
- * Jammy has a malloc() performance degradation
-if CPU affinity masks are used (not default).
+ * Jammy
** Description changed:
- https://sourceware.org/bugzilla/show_bug.cgi?id=30945
+ [Impact]
+
+ * Jammy has a malloc() performance degradation
+if CPU affinity masks are used (not default).
+
+ * The maximum number of arenas for malloc() is
+calculated based on the number of processors.
Now with the patch [1] applied, it is back to normal.
$ dpkg -s libc6 | grep Version:
Version: 2.35-0ubuntu3.8+gd47c5e4db792
Without per-CPU affinity (average: 63ms) -- no regression
$ ./test-glibc-malloc 56 false false
nr_cpu: 56 pin: no fix: no
thread average (ms): 69.9
Some snippets (more line breaks for clarity) from
https://sourceware.org/bugzilla/show_bug.cgi?id=30945
"""
<...> The deserialization library we used works 10x slower than
expected.
Investigations show that this is due to the arena_get2 function uses
__get_nprocs_
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Title:
malloc performance degradation with CPU affinity masks
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Reproducer with a Jammy LXD container.
System with 56 processors ("threads").
LXD and gcc setup:
$ lxc launch ubuntu:jammy glibc-jammy
$ lxc exec glibc-jammy -- su - ubuntu
$ wget -O test-glibc-malloc.c
https://sourceware.org/bugzilla/attachment.cgi?id=15156
$ su
Checking for required dependencies of the last commit above:
---
Commits in-between the first offender and final fix, in the development
branch:
$ git log --oneline origin/master --
sysdeps/unix/sysv/linux/getsysstats.c | grep -v 'Update copyright dates'
472894d2cfee malloc: Use
Related git commits, starting with the first related change, and finishing with
the fix required.
The intermediary commits provide some context used later to understand the
required dependencies.
---
The initial commit changed __get_nprocs() to use sched_getaffinity()
instead of sysfs and procfs
** Description changed:
- WIP.
+ https://sourceware.org/bugzilla/show_bug.cgi?id=30945
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https://bugs.launchpad.net/bugs/2089789
Title:
malloc performance degradation with CPU affinity
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