Red Hat Bugzilla – Full Text Bug Listing
|Summary:||glibc: malloc may fall back to calling mmap prematurely if arenas are contended|
|Product:||Red Hat Enterprise Linux 7||Reporter:||Siddhesh Poyarekar <spoyarek>|
|Component:||glibc||Assignee:||Carlos O'Donell <codonell>|
|Status:||CLOSED ERRATA||QA Contact:||Arjun Shankar <ashankar>|
|Version:||7.3||CC:||ashankar, fweimer, mcermak, mkolar, mnewsome, pfrankli|
|Fixed In Version:||Doc Type:||Bug Fix|
Cause: In a low-memory situation, a logic error causes glibc malloc to use mmap even if memory is available internally without requesting it from the kernel. Consequence: The malloc implementation in glibc could use excessively rely on mmap, resulting performance problems. Fix: The logic error is corrected and available memory is reused. Result: Application performance in low-memory situations should improve.
|:||1348620 (view as bug list)||Environment:|
|Last Closed:||2016-11-03 04:25:03 EDT||Type:||Bug|
|oVirt Team:||---||RHEL 7.3 requirements from Atomic Host:|
|Bug Depends On:||1348620|
|Bug Blocks:||1297579, 1313485|
Description Siddhesh Poyarekar 2015-08-21 12:00:41 EDT
Description of problem: Due to the robust malloc changes, malloc functions may end up calling mmap prematurely if all arenas are contended but not corrupt. This is not a serious issue in the general case and its performance impact is also questionable because it is not clear if the contention is more expensive in terms of time than a system call. It is however expensive resource-wise if the block requests are significantly smaller than page size because that will create a lot of external holes. See also: bug 1246713 for rhel-6, where this problem is one of two problems that the bug report mentioned.
Comment 6 Florian Weimer 2016-06-21 11:10 EDT
Created attachment 1170318 [details] glibc-rh1245731-4.patch This is the patch which went into rhel-6.7.z.
Comment 7 Florian Weimer 2016-06-21 11:22:21 EDT
Proposed upstream fix: https://sourceware.org/ml/libc-alpha/2016-06/msg00815.html
Comment 8 Florian Weimer 2016-06-21 15:40:45 EDT
Comment 14 errata-xmlrpc 2016-11-03 04:25:03 EDT
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://rhn.redhat.com/errata/RHSA-2016-2573.html