linux-kernel - Re: slow performance on disk/network i/o full speed after drop

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Date:	Fri, 26 Aug 2011 11:03:13 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>
Cc:	Pekka Enberg <penberg@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>, Jens Axboe <jaxboe@...ionio.com>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: slow performance on disk/network i/o full speed after
 drop_caches

On Fri, Aug 26, 2011 at 10:54:35AM +0800, Stefan Priebe - Profihost AG wrote:
> Hi Wu,
> 
> > Ah you are running an older kernel that didn't show all the vmstat
> > numbers. But still it's revealing that node 0 is used heavily and node
> > 1 is almost idle. So I won't be surprised to see most free pages lie
> > in node 1.
> I'm running a 2.6.38 kernel.
> 
> There is at least a numastat proc file.

Thanks. This shows that node0 is accessed 10x more than node1.

> grep . /sys/devices/system/node/node*/numastat
> /sys/devices/system/node/node0/numastat:numa_hit 5958586
> /sys/devices/system/node/node0/numastat:numa_miss 0
> /sys/devices/system/node/node0/numastat:numa_foreign 0
> /sys/devices/system/node/node0/numastat:interleave_hit 4191
> /sys/devices/system/node/node0/numastat:local_node 5885189
> /sys/devices/system/node/node0/numastat:other_node 73397
> /sys/devices/system/node/node1/numastat:numa_hit 488922
> /sys/devices/system/node/node1/numastat:numa_miss 0
> /sys/devices/system/node/node1/numastat:numa_foreign 0
> /sys/devices/system/node/node1/numastat:interleave_hit 4187
> /sys/devices/system/node/node1/numastat:local_node 386741
> /sys/devices/system/node/node1/numastat:other_node 102181
> 
> >> modified it a little bit:
> >> ~# while [ true ]; do ps -eo
> >> user,pid,tid,class,rtprio,ni,pri,psr,pcpu,vsz,rss,pmem,stat,wchan:28,cmd
> >> | grep scp | grep -v grep; sleep 1; done
> >>
> >> root     12409 12409 TS       -   0  19   0 59.8  42136  1724  0.0 Ss
> >> poll_schedule_timeout        scp -t /tmp/
> >
> > It's mostly doing poll() waits. There must be some dependency on
> > something other to make progress. Would you post the full ps output
> > for all tasks, and even better, run
> complete ps output:
> http://pastebin.com/raw.php?i=b948svzN

In that log, scp happens to be in R state and also no other tasks in D
state. Would you retry in the hope of catching some stucked state?

> >          echo t>  /proc/sysrq-trigger
> sadly i wa sonly able to grab the output in this crazy format:
> http://pastebin.com/raw.php?i=MBXvvyH1

It's pretty readable dmesg, except that the data is incomplete and
there are nothing valuable in the uploaded portion..

Thanks,
Fengguang
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