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From: "cfester at tmriusa dot com" <sourceware-bugzilla@sourceware.org> To: glibc-bugs@sourceware.org Subject: [Bug string/16830] memset performance regression Date: Fri, 16 Oct 2015 04:39:00 -0000 [thread overview] Message-ID: <bug-16830-131-cPKuNkjK0l@http.sourceware.org/bugzilla/> (raw) In-Reply-To: <bug-16830-131@http.sourceware.org/bugzilla/> https://sourceware.org/bugzilla/show_bug.cgi?id=16830 --- Comment #5 from Chris Fester <cfester at tmriusa dot com> --- We also have seen a performance regression in memset. Our previous system software used eglibc 2.15. When we were evaluating Yocto 1.6, we started using eglibc 2.19 and saw the problem. We continued to see it with glibc 2.21 when using Yocto 1.8. Our system software frequently uses memset to initialize large areas of memory. We break up the memory area into chunks and dedicate all 16 cores to memset-ing a chunk. This likely thrashes the caches quite a bit, although I'll admit I haven't looked at any performance counters. For Yocto 1.6 we patched eglibc to revert to the unrolled loop version of memset.S. For Yocto 1.8, we actually produced a patch strikingly similar to Michael Matz's patch to fix the regression. Some hardware details: CPU - 2 Sandy Bridge based Xeon CPUs, 16 cores total Memory - 32 GB on each node I attached a c source file to do some cycle counting for memset with multiple threads. If I have time tomorrow I will attach an ODS spreadsheet with a graph illustrating the data we collected, as well as the patch we're currently using to work around the problem. Please let us know how we can help with this issue. Thanks, Chris Fester -- You are receiving this mail because: You are on the CC list for the bug.
next prev parent reply other threads:[~2015-10-16 4:39 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-04-10 16:04 [Bug libc/16830] New: " schwab@linux-m68k.org 2014-04-28 8:12 ` [Bug libc/16830] " neleai at seznam dot cz 2014-05-21 12:55 ` matz at suse dot de 2014-05-21 14:21 ` matz at suse dot de 2014-06-12 19:43 ` fweimer at redhat dot com 2015-08-27 22:21 ` [Bug string/16830] " jsm28 at gcc dot gnu.org 2015-10-16 3:55 ` cfester at tmriusa dot com 2015-10-16 4:39 ` cfester at tmriusa dot com [this message] 2024-05-09 19:16 ` hjl.tools at gmail dot com
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