Messages in this thread | | | Date | Fri, 28 Mar 2008 10:28:56 +0100 | From | Ingo Molnar <> | Subject | Re: Performance changes between 2.6.13 and 2.6.23 |
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* Sanders, Rob M. <sanders-rob@zai.com> wrote:
> Sorry to disappear for a few days, I just hadn't had time to do > anything at home. Finally had some time to run some test, and at this > point I'm thinking that the problem is not with the kernel. Not quite > sure where to look next, but I've done the following tests: > > YDL4.0.91 with 2.6.13 kernel - normal speed > YDL6.0 with 2.6.23 kenrel - 4-5x slowdown > YDL4.1 with 2.6.15 kernel - 4-5x slowdown > YDL4.0.91 with 2.6.15 kernel - *normal speed* - kernel config pulled from YDL4.1 install > YDL4.0.91 with 2.6.23 kernel - failed boot
if you suspect the scheduler then please try the following suggestions i made in another thread:
----------> could you run this script while such a slowdown is really prominent:
http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh
and send me the output it generates? The output is the most useful if you do this on a kernel that has CONFIG_SCHED_DEBUG=y and CONFIG_SCHEDSTATS=y enabled.
on the off chance that this issue has been fixed in the soon-to-be 2.6.25 kernel, you might also want to try x86.git/latest, which is based on the latest Linus tree and has all relevant x86 fixes and improvements added as well: http://people.redhat.com/mingo/x86.git/README
several of the changes can affect performance.
a third (and most comprehensive) way to debug this would be to send me a scheduler trace of such a slowdown, you can generate a scheduler trace the following way:
http://people.redhat.com/mingo/sched-devel.git/readme-tracer.txt
but we can probably give a first estimation based on the cfs-debug-info output already. Btw., you can combine the scheduler and the x86 git tree into a temporary unified tree by doing these two commands:
git-checkout -b tmp x86/latest git-merge sched-devel/latest
(run "make oldconfig" to pick up the new config options.)
Ingo
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