Re: isolate_freepages_block and excessive CPU usage by OSD process

[Joonsoo Kim <iamjoonsoo.kim@lge.com>]

On Tue, Nov 25, 2014 at 01:48:42AM +0400, Andrey Korolyov wrote:
> On Sun, Nov 23, 2014 at 12:33 PM, Christian Marie <christian@ponies.io> wrote:
> > Here's an update:
> >
> > Tried running 3.18.0-rc5 over the weekend to no avail. A load spike through
> > Ceph brings no perceived improvement over the chassis running 3.10 kernels.
> >
> > Here is a graph of *system* cpu time (not user), note that 3.18 was a005.block:
> >
> > http://ponies.io/raw/cluster.png
> >
> > It is perhaps faring a little better that those chassis running the 3.10 in
> > that it did not have min_free_kbytes raised to 2GB as the others did, instead
> > it was sitting around 90MB.
> >
> > The perf recording did look a little different. Not sure if this was just the
> > luck of the draw in how the fractal rendering works:
> >
> > http://ponies.io/raw/perf-3.10.png
> >
> > Any pointers on how we can track this down? There's at least three of us
> > following at this now so we should have plenty of area to test.
> 
> 
> Checked against 3.16 (3.17 hanged for an unrelated problem), the issue
> is presented for single- and two-headed systems as well. Ceph-users
> reported presence of the problem for 3.17, so probably we are facing
> generic compaction issue.
> 

Hello,

I didn't follow-up this discussion, but, at glance, this excessive CPU
usage by compaction is related to following fixes.

Could you test following two patches?

If these fixes your problem, I will resumit patches with proper commit
description.

Thanks.

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