Bug 1255822 – glibc: malloc may fall back to calling mmap prematurely if arenas are contended

Bugzilla will be upgraded to version 5.0. The upgrade date is tentatively scheduled for 2 December 2018, pending final testing and feedback.

Bug 1255822 - glibc: malloc may fall back to calling mmap prematurely if arenas are contended

Summary:	glibc: malloc may fall back to calling mmap prematurely if arenas are contended

Status:	CLOSED ERRATA

Aliases:	None

Product:	Red Hat Enterprise Linux 7
Classification:	Red Hat
Component:	glibc (Show other bugs)
Sub Component:
Version:	7.3
Hardware:	Unspecified Unspecified

Priority	unspecified Severity unspecified
Target Milestone:	rc
Target Release:	---
Assigned To:	Carlos O'Donell
QA Contact:	Arjun Shankar
Docs Contact:

URL:
Whiteboard:
Keywords:	Patch

Depends On:	1348620
Blocks:	1297579 1313485
	Show dependency tree / graph

Reported:	2015-08-21 12:00 EDT by Siddhesh Poyarekar
Modified:	2017-01-25 07:00 EST (History)
CC List:	6 users (show)

See Also:	1246713
Fixed In Version:
Doc Type:	Bug Fix
Doc Text:	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.
Story Points:	---
Clone Of:
Clones:	1348620 (view as bug list)
Environment:
Last Closed:	2016-11-03 04:25:03 EDT
Type:	Bug
Regression:	---
Mount Type:	---
Documentation:	---
CRM:
Verified Versions:
Category:	---
oVirt Team:	---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---

Attachments	(Terms of Use)
glibc-rh1245731-4.patch (1.38 KB, patch) 2016-06-21 11:10 EDT, Florian Weimer	no flags	Details \| Diff
Add an attachment (proposed patch, testcase, etc.)

External Trackers
Tracker	ID	Priority	Status	Summary	Last Updated
Sourceware	20284	None	None	None	2016-06-21 10:49 EDT
Red Hat Product Errata	RHSA-2016:2573	normal	SHIPPED_LIVE	Low: glibc security, bug fix, and enhancement update	2016-11-03 08:05:56 EDT

Groups: None (edit)

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

Upstream commit: https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=a3b473373ee43a292f5ec68a7fda6b9cfb26a9b0

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

Note You need to log in before you can comment on or make changes to this bug.