Messages in this thread |  | | | Date | Tue, 21 Feb 2012 20:42:43 -0500 | | From | Josh Boyer <> | | Subject | Re: Large slowdown with 'x86: Avoid invoking RCU when CPU is idle' |
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On Tue, Feb 21, 2012 at 05:32:52PM -0800, Paul E. McKenney wrote: > On Tue, Feb 21, 2012 at 08:16:53PM -0500, Josh Boyer wrote: > > Hi Paul, > > > > Over in Fedora land, I applied your patch from this thread: > > > > https://lkml.org/lkml/2012/1/24/441 > > > > to our 3.3-rc3/rc4 based rawhide kernels. The intention was to solve an > > RCU issue that was very similar to what Eric originally reported, and > > the RCU splat did indeed go away[1]. > > > > However, we then got a few reports of kernels containing that patch > > being extremely slow. When the patch was dropped, the slowness goes > > away according to one reporter. The details can be found in this bug: > > > > https://bugzilla.redhat.com/show_bug.cgi?id=795050 > > > > The slowness doesn't seem to hit everyone, and in my local testing > > things seem to be working just fine. The reporters have widely varying > > hardware as well, so it doesn't seem machine specific. > > > > Perhaps I misdiagnosed the original issue, or perhaps I missed something > > else that needs to be applied prior to this but I thought I would point > > this out in case you had any ideas.
First off, thanks for the quick reply!
> This patch has been obsoleted by patches #45-47 in this series: > > https://lkml.org/lkml/2012/2/3/459
Holy lots of patches...
> And patch #47 in that series has been obsoleted by another series > from Steven Rostedt: > > https://lkml.org/lkml/2012/2/7/231
Ok.
> Hopefully these fix both splats and slowness.
So again, I'm slightly confused on how RCU patches flow. Eric originally reported the bug for which you created the patch I applied against 3.3. The giant patch series above seems queued for 3.4.
I don't see stable CC'd on 45-47, nor any of Steven's patches. I doubt I'd want to go applying the 47-patch series on 3.3 at the moment, and given you have these marked for 3.4 I don't think you do either. However, is there some kind of fix for the original bug report against 3.3?
josh
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