linux-kernel - Re: 3.12-rcX - NFS regression - kswapd0 / kswapd1 stays using 100% CPU?

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Date:	Thu, 17 Oct 2013 21:07:30 +0000
From:	"Myklebust, Trond" <Trond.Myklebust@...app.com>
To:	Helge Deller <deller@....de>
CC:	Linux Kernel Development <linux-kernel@...r.kernel.org>,
	NFS list <linux-nfs@...r.kernel.org>,
	list parisc-linux <parisc-linux@...ts.parisc-linux.org>
Subject: Re: 3.12-rcX - NFS regression - kswapd0 / kswapd1 stays using 100%
 CPU?

On Thu, 2013-10-17 at 22:42 +0200, Helge Deller wrote:
> I'm seeing a regression with current kernel git head when using NFS-mounts.
> Architecture in my case is parisc, although I don't think that this is relevant.
> At least kernel 3.10 (and I think 3.11) didn't showed that problem.
> 
> The symtom is, that "top" shows high usage of either kswapd0 or kswapd1.
> Here is an output with kswapd1:
>   PID USER      PR  NI  VIRT  RES  SHR S  %CPU %MEM     TIME+ COMMAND
>    37 root      20   0     0    0    0 R  91.8  0.0  63:00.40 kswapd1
> 28448 root      20   0  3252 1428 1060 R  15.3  0.0   0:00.09 top
>     1 root      20   0  2784  988  852 S   0.0  0.0   0:09.95 init
> 
> This is what ps shows:
> lsXXXX:~# ps -ef |  grep mount
> root      1181     1  0 14:51 ?        00:00:18 /usr/sbin/automount --pid-file /var/run/autofs.pid
> root     25331  1181  0 21:25 ?        00:00:00 /bin/mount -n -t nfs -s -o nolock,rw,hard,intr homes:/unixhome1 /net/home1
> root     25332 25331  0 21:25 ?        00:00:00 /sbin/mount.nfs homes:/unixhome1 /net/home1 -s -n -o rw,nolock,hard,intr
> 
> And using sysrq to show the blocked tasks I get in syslog:
> SysRq : Show Blocked State
> mount.nfs       D 00000000401040c0     0 25332  25331 0x00000010
> Backtrace:
> [<0000000040113a68>] __schedule+0x500/0x810
> 
> I know it's not a problem of the NFS server, since the same mount is still ok on other machines.
> The NFS directory was already mounted and in use when this mount happened again (called by cron-job). 
>  
> Any ideas?

If the NFS directory is already mounted, then why is the automounter
trying to mount it a second time?

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@...app.com
www.netapp.com
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