A Significant Linux 4.7 Kernel Performance Regression Has Now Been Resolved
Written by Michael Larabel in Linux Kernel on 26 June 2016 at 08:19 AM EDT. 4 Comments
LINUX KERNEL --
There was a 30~40% drop in some of the SPEC Java benchmarks when using the Linux 4.7 development code, but fortunately this regression has now been discovered and addressed.

Fortunately this huge regression didn't make it into a released kernel but was the 4.7 development code relative to Linux 4.6. The issue was first reported ten days ago and the developers had been working to figure out the problem up until this weekend when it appears everything is now squared away.

The SPECjbb2005 and SPECjvm2008 benchmarks were seeing 30~40% performance drops with Linux 4.7 RCs relative to Linux 4.6 and the issue ocurred on a variety of different servers.

The good news is this problem has been tracked down to a scheduler issue that was introduced during the Linux 4.7 merge window. The code is now in sched/urgent and thus will be fixed for Linux 4.7 final.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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