A Significant Linux 4.7 Kernel Performance Regression Has Now Been Resolved

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.