linux-kernel - Re: Horrible btrfs performance on cold cache

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Message-ID: <AANLkTinYz59U1hZd=C=zaTkJOvU93Vnb31bS1GkAHByA@mail.gmail.com>
Date:	Mon, 11 Oct 2010 11:24:16 -0500
From:	Chester <somethingsome2000@...il.com>
To:	Calvin Walton <calvin.walton@...il.com>
Cc:	Felipe Contreras <felipe.contreras@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-btrfs@...r.kernel.org, Chris Mason <chris.mason@...cle.com>
Subject: Re: Horrible btrfs performance on cold cache

I think I read/heard somewhere that snapshots can cause pretty bad
fragmentation, because it causes your system to write changes to files
to random locations on the disk, leaving the original inodes intact..
For that reason, I have replaced the directories ~/.config/chromium ,
/var , /usr/portage with subvolumes, so they will not be included in
snapshots.

It seems like chromium opens much quicker now, but it's still a long
way from what it was on ext4

On Mon, Oct 11, 2010 at 10:46 AM, Calvin Walton <calvin.walton@...il.com> wrote:
>
> On Mon, 2010-10-11 at 03:30 +0300, Felipe Contreras wrote:
> > Hi,
> >
> > I use btrfs on most of my volumes on my laptop, and I've always felt
> > booting was very slow, but definitely sure is slow, is starting up
> > Google Chrome:
> >
> > encrypted ext4: ~20s
> > btrfs: ~2:11s
> >
> > I have tried different things to find out exactly what is the issue,
> > but haven't quite found it yet.
>
> If you've been using this volume for a while, it could just have become
> badly fragmented. You could try btrfs's fancy online defragmentation
> abilities to see if that'll give you an improvement:
>
> # btrfs filesystem defragment /mountpoint/of/volume
>
> Let us know if that helps, of course :)
>
> --
> Calvin Walton <calvin.walton@...il.com>
>
> --
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