linux-ext4 - Re: Slow filesystem.

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Message-ID: <20110514054553.GB6028@bitwizard.nl>
Date:	Sat, 14 May 2011 07:45:53 +0200
From:	Rogier Wolff <R.E.Wolff@...Wizard.nl>
To:	Andreas Dilger <adilger@...ger.ca>
Cc:	Rogier Wolff <R.E.Wolff@...Wizard.nl>, linux-ext4@...r.kernel.org
Subject: Re: Slow filesystem.

On Fri, May 13, 2011 at 11:21:52PM -0600, Andreas Dilger wrote:
> On May 13, 2011, at 06:59, Rogier Wolff wrote:
> > My work (as in what brings in money to buy things from) file-system is
> > now "slow as hell". Last time this happened you guys told me that this
> > was because I had millions of hardlinks and way too many files.
> > 
> > Filesystem            Inodes   IUsed   IFree IUse% Mounted on
> > /dev/md0                815M    4.1M    811M    1% /recover2
> > 
> > I have only 4.1M files. Only 1% inodes "in use". 
> > 
> > 
> > The filesystem was filling up lately, but i've managed to create some
> > free space.
> > 
> > Filesystem            Size  Used Avail Use% Mounted on
> > /dev/md0              6.3T  5.3T  720G  89% /recover2

> I suspect that the free inodes in your filesystem are very
> fragmented, due to the filesystem filling up and then deleting a lot
> of files that create "holes" of free inodes within the inode table
> blocks.  That means that possibly finding free inodes is a bunch of
> work, and then possibly only one or two inodes are allocated from
> each block.

How can the free inodes be fragmented?!? 99% of the available inodes
ARE free.

> > The question is: How do I get the filesystem to perform
> > normally again?
 
> It is probably worthwhile to do a blktrace to see what the IO is
> looking like, and as Eric suggested the oprofile information may be
> interesting if a lot of CPU is being used.

A lot of CPU time is being used, yes. The 62 milliseconds are almost
completely CPU time.

I was running a big "backup" (image of a 500Gb disk) onto the
partition. Now that this has finished I'll try booting into a recent
kernel. Next I'll try finding and applying the patch.... 

	Roger.

-- 
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