linux-kernel - Re: [PATCH] Give kjournald a IOPRIO_CLASS

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Date:	Thu, 2 Oct 2008 21:45:11 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Jens Axboe <jens.axboe@...cle.com>, linux-kernel@...r.kernel.org,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH] Give kjournald a IOPRIO_CLASS_RT io priority

On Thu, 2 Oct 2008 21:40:00 -0700
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Thu, 2 Oct 2008 21:23:55 -0700 Arjan van de Ven
> <arjan@...radead.org> wrote:
> 
> > On Thu, 2 Oct 2008 21:01:17 -0700
> > Arjan van de Ven <arjan@...radead.org> wrote:
> > 
> > > > _
> > > > 
> > > > perhaps for varying values of "1".
> > > 
> > 
> > caught a few, a few were over 3 1/2 seconds in stall time 
> > (specifically I know this for the last one)
> > 
> > (I've stripped out the ? entries to keep them reasonable)
> > 
> > [  410.168277] WARNING: at kernel/sched.c:5652
> > io_schedule+0x77/0xb0() [  410.168347] Pid: 699, comm: kjournald
> > Not tainted 2.6.27-rc8-tip #50 [  410.168366]  [<c042ee64>]
> > warn_on_slowpath+0x41/0x65 [  410.168414]  [<c070ec83>]
> > io_schedule+0x77/0xb0 [  410.168421]  [<c04abc72>]
> > sync_buffer+0x33/0x37 [  410.168429]  [<c070f123>]
> > __wait_on_bit+0x36/0x5d [  410.168445]  [<c070f1f5>]
> > out_of_line_wait_on_bit+0xab/0xb3 [  410.168471]  [<c04abbd1>]
> > __wait_on_buffer+0x19/0x1c [  410.168478]  [<c04de796>]
> > journal_commit_transaction+0x484/0xcb2 [  410.168519]  [<c04e14ae>]
> > kjournald+0xc7/0x1ea [  410.168544]  [<c043fb87>] kthread+0x3b/0x61
> > [  410.168559]  [<c040499f>] kernel_thread_helper+0x7/0x10
> > [  410.168567]  =======================
> > [  410.168572] ---[ end trace de523043f88bd9a7 ]---
> > [  451.605034] ------------[ cut here ]------------
> > [  451.605041] WARNING: at kernel/sched.c:5652
> > io_schedule+0x77/0xb0() [  451.605114] Pid: 699, comm: kjournald
> > Tainted: G        W 2.6.27-rc8-tip #50
> >
> > ...
> >
> 
> hm, they're all kjournald getting stuck on lock_buffer().  That _may_
> be related to the one we care about, but it doesn't seem likely.

one of them is (based on timestamps of the printk) is less than 3
seconds before the "real" one, while the real one's delay was 4 seconds.
To me that implies they're at least somewhat correlated...


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
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