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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.

Created attachment 1170318 [details]
glibc-rh1245731-4.patch

This is the patch which went into rhel-6.7.z.

Proposed upstream fix: https://sourceware.org/ml/libc-alpha/2016-06/msg00815.html

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

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