linux-kernel - Re: System CPU increasing on idle 2.6.36

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Date:	Tue, 4 Jan 2011 13:40:08 -0800
From:	Simon Kirby <sim@...tway.ca>
To:	Mark Moseley <moseleymark@...il.com>
Cc:	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: System CPU increasing on idle 2.6.36

On Tue, Jan 04, 2011 at 09:42:14AM -0800, Mark Moseley wrote:

> On Wed, Dec 29, 2010 at 2:03 PM, Simon Kirby <sim@...tway.ca> wrote:
>
> > I've noticed nfs_inode_cache is ever-increasing as well with 2.6.37:
> >
> > ?OBJS ACTIVE ?USE OBJ SIZE ?SLABS OBJ/SLAB CACHE SIZE NAME
> > 2562514 2541520 ?99% ? ?0.95K ?78739 ? ? ? 33 ? 2519648K nfs_inode_cache
> > 467200 285110 ?61% ? ?0.02K ? 1825 ? ? ?256 ? ? ?7300K kmalloc-16
> > 299397 242350 ?80% ? ?0.19K ?14257 ? ? ? 21 ? ? 57028K dentry
> > 217434 131978 ?60% ? ?0.55K ? 7767 ? ? ? 28 ? ?124272K radix_tree_node
> > 215232 ?81522 ?37% ? ?0.06K ? 3363 ? ? ? 64 ? ? 13452K kmalloc-64
> > 183027 136802 ?74% ? ?0.10K ? 4693 ? ? ? 39 ? ? 18772K buffer_head
> > 101120 ?71184 ?70% ? ?0.03K ? ?790 ? ? ?128 ? ? ?3160K kmalloc-32
> > ?79616 ?59713 ?75% ? ?0.12K ? 2488 ? ? ? 32 ? ? ?9952K kmalloc-128
> > ?66560 ?41257 ?61% ? ?0.01K ? ?130 ? ? ?512 ? ? ? 520K kmalloc-8
> > ?42126 ?26650 ?63% ? ?0.75K ? 2006 ? ? ? 21 ? ? 32096K ext3_inode_cache
> >
> > http://0x.ca/sim/ref/2.6.37/inodes_nfs.png
> > http://0x.ca/sim/ref/2.6.37/cpu2_nfs.png
> >
> > Perhaps I could bisect just fs/nfs changes between 2.6.35 and 2.6.36 to
> > try to track this down without having to wait too long, unless somebody
> > can see what is happening here.
> 
> I'll get started bisecting too, since this is something of a
> show-stopper. Boxes that pre-2.6.36 would stay up for months at a time
> now have to be powercycled every couple of days (which is about how
> long it takes for this behavior to show up). This is across-the-board
> for about 50 boxes, ranging from 2.6.36 to 2.6.36.2.
> 
> Simon: It's probably irrelevant since these are kernel threads, but
> I'm curious what distro your boxes are running. Ours are Debian Lenny,
> i386, Dell Poweredge 850s. Just trying to figure out any
> commonalities. I'll get my boxes back on 2.6.36.2 and start watching
> nfs_inode_cache as well.

Same distro, x86_64, similar servers.

I'm not sure if the two cases I am seeing are exactly the same problem,
but on the log crunching boxes, system time seems proportional to
nfs_inode_cache and nfs_inode_cache just keeps growing forever; however,
if I stop the load and unmount the NFS mount points, all of the
nfs_inode_cache objects do actually go away (after umount finishes).

It seems the shrinker callback might not be working as intended here.

On the shared server case, the crazy spinlock contention from all of the
flusher processes happens suddenly and overloads the boxes for 10-15
minutes, and then everything recovers.  Over 21 of these boxes, they
each have about 500k-700k nfs_inode_cache objects.  The log cruncher hit
3.3 million nfs_inode_cache objects before I unmounted.

Are your boxes repeating this behaviour at any predictable interval?

Simon-
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