RE: fsync occasionally very slow

["Matthew Kirk" <mkirk01@rcn.com>]

Sorry, this will show my ignorance...  my system is lacking
/proc/sysrq-trigger.  I can find how to build a kernel with the magic sysrq
key (CONFIG_MAGIC_SYSRQ=y), and have done so, but I still don't have
/proc/sysrq-* and cannot seem to find how to build in sysrq functionality
itself - assuming that's what's missing.  Presumably it's something in
.config I'm just not seeing?

Thanks again!

Matt

-----Original Message-----
From: Andrew Morton [mailto:akpm@osdl.org] 
Sent: Friday, January 26, 2007 6:17 AM
To: Matthew Kirk
Cc: linux-kernel@vger.kernel.org
Subject: Re: fsync occasionally very slow

On Fri, 26 Jan 2007 05:37:38 -0500
"Matthew Kirk" <mkirk01@rcn.com> wrote:

> I am working on an application that fsync(2) files and directories as
> needed.    I’m seeing intermittent stalls on fsync that can last many
> seconds.

Please generate an all-task backtrace during the stall via:

dmesg -n 8
<wait for a stall>
echo t > /prov/sysrq-trigger
dmesg -s 1000000 > foo

and send foo.

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