linux-kernel - Re: Linux 2.6.29

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Message-ID: <49D625A0.1030202@rtr.ca>
Date:	Fri, 03 Apr 2009 11:05:04 -0400
From:	Mark Lord <lkml@....ca>
To:	Lennart Sorensen <lsorense@...lub.uwaterloo.ca>
Cc:	Jens Axboe <jens.axboe@...cle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>, tytso@....edu,
	drees76@...il.com, jesper@...gh.cc,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Linux 2.6.29

Lennart Sorensen wrote:
>
> Well the system is setup like this:
> 
> Core 2 Quad Q6600 CPU (2.4GHz quad core).
> Asus P5K mainboard (Intel P35 chipset)
> 6GB of ram
> PVR500 dual NTSC tuner pci card
..
> So the behaviour with cfq is:
> Disk light seems to be constantly on if there is any disk activity.  iotop
> can show a total io of maybe 1MB/s and the disk light is on constantly.
..

Lennart,

I wonder if the problem with your system is really a Myth/driver issue?

Curiously, I have a HVR-1600 card here, and when recording analog TV with
it the disk lights are on constantly.  The problem with it turns out to
be mythbackend doing fsync() calls ten times a second.

My other tuner cards don't have this problem.

So perhaps the PVR-500 triggers the same buggy behaviour as the HVR-1600?
To work around it here, I decided to use a preload library that replaces
the frequent fsync() calls with a more moderated behaviour:

   http://rtr.ca/hvr1600/libfsync.tar.gz

Grab that file and try it out.  Instructions are included within.
Report back again and let us know if it makes any difference.

Someday I may try and chase down the exact bug that causes mythbackend
to go fsyncing berserk like that, but for now this workaround is fine.

Cheers
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