linux-kernel - Re: Linux 2.6.29

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Date:	Mon, 6 Apr 2009 10:06:44 -0400
From:	lsorense@...lub.uwaterloo.ca (Lennart Sorensen)
To:	Jeff Garzik <jeff@...zik.org>
Cc:	Janne Grunau <j@...nau.net>, David Rees <drees76@...il.com>,
	Mark Lord <lkml@....ca>, 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,
	jesper@...gh.cc,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Linux 2.6.29

On Sat, Apr 04, 2009 at 07:02:51PM -0400, Jeff Garzik wrote:
> Is dd + sync_file_range really a realistic comparison?  dd is streaming  
> as fast as the disk can output data, whereas MythTV is streaming as fast  
> as video is being recorded.  If you are maxing out your disk throughput,  
> there will be obvious impact no matter what.
>
> I would think a more accurate comparison would be recording multiple  
> video streams in parallel, comparing fsync/fdatasync/sync_file_range?
>
> IOW, what is an average MythTV setup -- what processes are actively  
> reading/writing storage?  Where are you noticing latencies, and does  
> sync_file_range decrease those areas of high latency?

I am going to give the patch a shot.  I run dual tuners after all, so
I do get multiple streams recording while doing playback at the same time.

-- 
Len Sorensen
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