Re: Performance Issues

[Rob Spanton <rob@robspanton.com>]

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Hi,

Thanks for the response everyone.

I wrote:
> I have a particularly uncomplicated setup (a desktop PC with a hard
> disk) and I'm seeing particularly slow performance from btrfs.  A `git
> status` in the linux source tree takes about 46 seconds after dropping
> caches, whereas on other machines using ext4 this takes about 13s.  My
> mail client (evolution) also seems to perform particularly poorly on
> this setup, and my hunch is that it's spending a lot of time waiting on
> the filesystem.

The evolution problem has been improved: the sqlite db that it was using
had over 18000 fragments, so I got evolution to recreate that file with
nocow set.  It now takes "only" 30s to load my mail rather than 80s,
which is better...

On Fri, 2014-09-19 at 11:05 -0400, Josef Bacik wrote:
> Weird, I get the exact opposite performance.  Anyway it's probably 
> because of your file layouts, try defragging your git dir and see if 
> that helps.  Thanks,

Defragging has improved matters a bit: it now takes 26s (was 46s) to run
git status.  Still not amazing, but at the moment I have no evidence to
suggest that it's not something to do with the machine's hardware.  If I
get time over the weekend I'll dig out an external hard disk and try a
couple of benchmarks with that.

For reference, these are the mount flags:
        /dev/sda4 on / type btrfs (rw,noatime,space_cache)
        /dev/sda4 on /home type btrfs (rw,noatime,space_cache)

Cheers,

Rob


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