linux-ext4 - Re: [PATCH] e2freefrag utility

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Date:	Fri, 24 Jul 2009 17:14:25 -0600
From:	Andreas Dilger <adilger@....com>
To:	Theodore Tso <tytso@....edu>
Cc:	Eric Sandeen <sandeen@...hat.com>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] e2freefrag utility

On Jul 24, 2009  18:32 -0400, Theodore Ts'o wrote:
> One question --- right now the chunksize (as specified by -c) only
> affects these lines printed by e2freefrag, right?
> 
> Chunksize: 1048576 bytes (256 blocks)
> Total chunks: 71681
> Free chunks: 21657 (30.2%)

Yes, pretty much.

> They are a little confusing since "chunk" as used here is different
> from "chunk" used in the next part of the output:
> 
> Min free chunk: 4 KB 
> Max free chunk: 568232 KB
> Avg free chunk: 188 KB

You're right.  "free extent" is better.

> How useful is it to print the "total chunks / free chunks" in the
> general case?  I'm guessing this relates to Lutsre's chunking and
> chunksize?

Well, it was important for the hardware RAID setups, to see how many
stripe-aligned free chunks are available in the filesystem.  Since
mballoc will also try to allocate/align on "chunk" boundaries this
is useful to know.  If this chunksize depended on the superblock
s_raid_stripe_width then it would be more useful for the general public.

> Would it make sense to only print the "Chunksize / Total
> chunks / Free Chunks" if a chunksize is specified explicitly via the
> -c option, and to do a s/chunk/extent/ in the next part of the output,

I don't have a big objection.  I don't think there are any tools that
depend on this output.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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