Re: How git affects kernel.org performance

From: Willy Tarreau <w@1wt.eu>
Date: Jan 7, 2007, 09:03 UTC
Message-ID: <20070107090336.GA7741@1wt.eu>
In-Reply-To: <45A0B63E.2020803@zytor.com>

On Sun, Jan 07, 2007 at 12:58:38AM -0800, H. Peter Anvin wrote:

Show 21 quoted lines

> Willy Tarreau wrote:
> >
> >At work, we had the same problem on a file server with ext3. We use rsync
> >to make backups to a local IDE disk, and we noticed that getdents() took
> >about the same time as Peter reports (0.2 to 2 seconds), especially in
> >maildir directories. We tried many things to fix it with no result,
> >including enabling dirindexes. Finally, we made a full backup, and switched
> >over to XFS and the problem totally disappeared. So it seems that the
> >filesystem matters a lot here when there are lots of entries in a
> >directory, and that ext3 is not suitable for usages with thousands
> >of entries in directories with millions of files on disk. I'm not
> >certain it would be that easy to try other filesystems on kernel.org
> >though :-/
> >
> 
> Changing filesystems would mean about a week of downtime for a server. 
> It's painful, but it's doable; however, if we get a traffic spike during 
> that time it'll hurt like hell.
> 
> However, if there is credible reasons to believe XFS will help, I'd be 
> inclined to try it out.

The problem is that I have no sufficient FS knowledge to argument why it helps here. It was a desperate attempt to fix the problem for us and it definitely worked well.

Hmmm I'm thinking about something very dirty : would it be possible to reduce the current FS size to get more space to create another FS ? Supposing you create a XX GB/TB XFS after the current ext3, you would be able to mount it in some directories with --bind and slowly switch some parts to it. The problem with this approach is that it will never be 100% converted, but as an experiment it might be worth it, no ?

Willy