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Re: Review: Concurrent Multi-File Data Streams

To: David Chinner <dgc@xxxxxxx>
Subject: Re: Review: Concurrent Multi-File Data Streams
From: Andi Kleen <andi@xxxxxxxxxxxxxx>
Date: 12 May 2007 20:46:19 +0200
Cc: xfs-dev <xfs-dev@xxxxxxx>, xfs-oss <xfs@xxxxxxxxxxx>
In-reply-to: <20070511003606.GB85884050@xxxxxxx>
References: <20070511003606.GB85884050@xxxxxxx>
Sender: xfs-bounce@xxxxxxxxxxx
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3
David Chinner <dgc@xxxxxxx> writes:
> 
> The following patch survives XFSQA with timeouts set to minimum,
> default, 500s and maximum. The patch has not had a great
> deal of low memory testing, and the object cache may need a shrinker
> interface to work in low memory conditions.
> 
> Comments?

It seems to be an optimization for a relatively small number of streams. When 
you
do a large number on average you should get similar readahead benefits
from round robing the streams over some AGs vs keeping it in a single AG,
right? 

The fallback to AG 0 if nstreams>AGs seems pretty lousy. Wouldn't it be better 
to do the normal XFS allocation algorithm then?  I think right now it will
go into low space mode in this case, which might give worse results.

Also centisecs is a really ugly unit whose use should be probably not 
propagated.

-Andi


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