linux-kernel - Re: IO latency

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Date:	Fri, 12 Jun 2009 23:51:19 -0600
From:	"Trenton D. Adams" <trenton.d.adams@...il.com>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Theodore Tso <tytso@....edu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: IO latency - a special case

On Fri, Jun 12, 2009 at 10:24 PM, Arjan van de Ven<arjan@...radead.org> wrote:
> On Fri, 12 Jun 2009 21:48:41 -0600
> "Trenton D. Adams" <trenton.d.adams@...il.com> wrote:
>
>> Sorry I didn't reply earlier.  I got busy with some server troubles
>> and such.
>> > What sort of process where you typicalling trying to kill using ^C?
>>
>> It's maven, which spawns javac (java compiler), as well as does
>> various other tasks such as making connections to the Internet, local
>> directories, etc.
>
> I assume you know latencytop and how it might be useful to diagnose
> such delays ?

Your assumption would be incorrect. ;)  Never heard of it before now.
But, I did have it installed for some reason.

However, when this starts happening, it's dang near impossible to do
anything on the machine.  I wouldn't be able to run it if I tried,
though I will try :D.  I barely have enough time to Ctrl-C before the
machines locks for about 3600 seconds.  And during that time (around
10-30 seconds), I can't really switch applications, as the latency is
so high.

Right now, just during normal system usage, it's showing...
Cause                                                Maximum     Percentage
poll_schedule_timeout do_sys_poll sys_poll sysente  5.0 msec         58.0 %
futex_wait do_futex compat_sys_futex sysenter_disp  5.0 msec         40.3 %
blk_execute_rq scsi_execute scsi_execute_req scsi_  3.9 msec          0.2 %
blk_execute_rq scsi_execute scsi_execute_req sd_re  3.5 msec          0.2 %
poll_schedule_timeout do_select core_sys_select sy  3.4 msec          0.3 %
blk_execute_rq scsi_execute scsi_execute_req sr_te  2.6 msec          0.5 %
blk_execute_rq scsi_execute scsi_execute_req sr_te  2.2 msec          0.5 %
blk_execute_rq scsi_execute sr_do_ioctl sr_packet   0.9 msec          0.1 %
blk_execute_rq scsi_execute scsi_execute_req ioctl  0.6 msec          0.0 %
release __blkdev_put blkdev_put blkdev_close __fput
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