linux-ext4 - Re: How git affects kernel.org performance

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Message-ID: <20070108141755.GF32756@thunk.org>
Date:	Mon, 8 Jan 2007 09:17:55 -0500
From:	Theodore Tso <tytso@....edu>
To:	Pavel Machek <pavel@....cz>
Cc:	Johannes Stezenbach <js@...uxtv.org>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Andrew Morton <akpm@...l.org>, Willy Tarreau <w@....eu>,
	Linus Torvalds <torvalds@...l.org>,
	"H. Peter Anvin" <hpa@...or.com>, git@...r.kernel.org,
	nigel@...el.suspend2.net, "J.H." <warthog9@...nel.org>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	kernel list <linux-kernel@...r.kernel.org>,
	webmaster@...nel.org,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: How git affects kernel.org performance

On Mon, Jan 08, 2007 at 02:59:52PM +0100, Pavel Machek wrote:
> Hi!
> 
> > > Would e2fsck -D help? What kind of optimization
> > > does it perform?
> > 
> > It will help a little; e2fsck -D compresses the logical view of the
> > directory, but it doesn't optimize the physical layout on disk at all,
> > and of course, it won't help with the lack of readahead logic.  It's
> > possible to improve how e2fsck -D works, at the moment, it's not
> > trying to make the directory be contiguous on disk.  What it should
> > probably do is to pull a list of all of the blocks used by the
> > directory, sort them, and then try to see if it can improve on the
> > list by allocating some new blocks that would make the directory more
> > contiguous on disk.  I suspect any improvements that would be seen by
> > doing this would be second order effects at most, though.
> 
> ...sounds like a job for e2defrag, not e2fsck...

I wasn't proposing to move other data blocks around in order make the
directory be contiguous, but just a "quick and dirty" try to make
things better.  But yes, in order to really fix layout issues you
would have to do a full defrag, and it's probably more important that
we try to fix things so that defragmentation runs aren't necessary in
the first place....

						- Ted

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