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Re: Zero filled files

To: Steve Lord <lord@xxxxxxx>
Subject: Re: Zero filled files
From: Andi Kleen <ak@xxxxxxx>
Date: Tue, 13 May 2003 18:37:31 +0200
Cc: Andi Kleen <ak@xxxxxxx>, linux-xfs@xxxxxxxxxxx
In-reply-to: <1052841045.22728.106.camel@jen.americas.sgi.com>
References: <20030512102338.GA3268@puariko.nirvana> <1052742135.1173.1.camel@laptop.americas.sgi.com> <20030513053133.GG10596@Wotan.suse.de> <1052839608.22728.104.camel@jen.americas.sgi.com> <20030513154629.GD26769@Wotan.suse.de> <1052841045.22728.106.camel@jen.americas.sgi.com>
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On Tue, May 13, 2003 at 10:50:45AM -0500, Steve Lord wrote:
> > > By adding the periodic actvity thread we activate some code which
> > > looks for an empty AIL and writes out a dummy log record to record
> > > the new tail of the log.
> > 
> > Does it check that it already wrote the marker before writing again ? 
> > If not the laptop users will hate you ;)
> 
> It does it twice, then stops

I would still suggest making the flush interval a sysctl and
provide the "SIGSTOP to stop thread until SIGCONT" interface. We did this
for ext3/jbd and it was very useful for laptops.

> > And I imagine changing this could add lots of seeking ...
> > (between the inode areas and the data areas) 
> 
> It may be more along the lines of holding off on letting the inode
> out to disk, but it would be complex.

I was thinking the same, but even with that it would add more seeking
I guess. Currently it would write out a lot of inodes in one go and then
later or earlier the extents.  With extent dependencies that would be split 
into multiple extent / inode writes with seeks inbetween.

-Andi


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