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

From: Helge Deller
Date: Thu Oct 31 2013 - 15:46:02 EST

On 10/19/2013 08:27 PM, Helge Deller wrote:
> On 10/18/2013 10:12 PM, Myklebust, Trond wrote:
>> On Fri, 2013-10-18 at 22:03 m, Helge Deller wrote:
>>> On 10/18/2013 09:36 PM, Myklebust, Trond wrote:
>>>> Also, could you please try a sysRQ-t the next time it happens, so that
>>>> we can get a trace of where the mount program is hanging. Knowing that
>>>> the mount is stuck in "__schedule()" is not really interesting unless we
>>>> know from where that was called.
>>> Actually, the machine was still running in this state.
>>> Here is sysrq-t:
>>> [112009.084000] mount S 00000000401040c0 0 25331 1 0x00000010
>>> [112009.084000] Backtrace:
>>> [112009.084000] [<0000000040113a68>] __schedule
>>> [112009.232000]
>>> [112009.232000] mount.nfs D 00000000401040c0 0 25332 25331 0x00000010
>>> [112009.232000] Backtrace:
>>> [112009.232000] [<0000000040113a68>] __schedule
>> That makes no sense unless sysrq-t works differently on parisc than on
>> other platforms. I'd expect the backtrace to at least include a system
>> call. Parisc experts?
> sysrq-t doesn't work differently on parisc. For other processes I do get
> a backtrace like the one on x86_64.
> That's the main reason why I asked for ideas here on the list.
> I do see the stuck process, but don't see any indications where it comes from.

I'm pretty sure that the regression (kswapd using 100% CPU) I reported here is fixed by this patch:

I will start some testing...

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