Subject : 2.6.25-rc1: volanoMark 45% regression
Submitter : "Zhang, Yanmin" <firstname.lastname@example.org>
Date : 2008-02-13 10:30
References : http://lkml.org/lkml/2008/2/13/128
Handled-By : Srivatsa Vaddagiri <email@example.com>
This entry is being used for tracking a regression from 2.6.24. Please don't
close it until the problem is fixed in the mainline.
Author: Srivatsa Vaddagiri <firstname.lastname@example.org>
Date: Fri Jan 25 21:08:00 2008 +0100
sched: group scheduling, change how cpu load is calculated
Handled-By : Balbir Singh <email@example.com>
References : http://lkml.org/lkml/2008/3/12/52
Peter reverted the load balance patch and 2.6.25-rc4 accepted the reverting patch.
With kernel 2.6.25-rc5, volanoMark has about 6% regression on my 16-core tigerton. If I apply patch http://lkml.org/lkml/2008/2/20/83 which fixes the tbench regression issue, volanoMark regression becomes about 4%.
I tried to bisect down which patch caused the last 4%, but found it's very hard. One thing is many patches depend on the reverted patches. The other thing is I find the testing result isn't stable since 2.6.25-rc1. The result variation might be more than 15% sometimes. I ran the testing against the same kernel for many times to get the best result.
I also tried to tune some sched_XXX parameters under /proc/sys/kernel, but didn't get better result than the default configuration.
Above regression exists on the 2.93GHz 16-core tigerton. With the less powerful 2.40GHz 16-core tigerton, the regression is less than 1%, but result is not stable and results of many runs might have about 15% variation.
On 8-core stoakley, the regression is about 1%.
References : http://lkml.org/lkml/2008/3/18/81
Author: Ingo Molnar <firstname.lastname@example.org>
Date: Fri Mar 14 22:16:08 2008 +0100
sched: fix fair sleepers
Fixed by: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=62fb185130e4d420f71a30ff59d8b16b74ef5d2b
According to comment #3 this commit was not enough for completely fixing the regression.