Re: [PATCH] fcache: a remapping boot cache

[Jens Axboe <axboe@suse.de>]

On Sat, Jun 24 2006, James wrote:
> Set this up on my laptop yesterday with some awesome results. I'm
> using 2.6.17-ck1 which has v2.1.
> 
> Heres some bootcharts, before, after, and a prime run.
> 
> http://archlinux.org/~james/normal.png
> http://archlinux.org/~james/fs-fcache.png
> http://archlinux.org/~james/fs-fcache-prime.png
> 
> Repeated boots show about the same 6 second improvement, 32 down to 26
> seconds. Looking at the slowdowns in the fs-fcache run, most are due
> to cpu load, waiting on network or, modprobe, and not disk access. X
> now starts nearly instantaneously.
> 
> As an experiment, I primed my cache right through to logging into my
> desktop environment. It was so effective, that now when I login, the
> GNOME splash screen only flickers onto the screen briefly, and the
> panels appear almost instantly. This is a big improvment over without
> fcache, where you'd see each component of GNOME being loaded on the
> splash screen, nautilus, metacity, and the panels would take quite a
> bit of time to render and load all their applets.
> 
> Impressive work, I hope to see it broadened to other filesystems,
> improved and merged to vanilla soon because it has clear improvements.

Thanks for giving it a spin! I have plans to implement some improvements
on monday that will speed it up even more, I hope I can talk you into
retesting it then. Basically it make sure we always get full speed out
of the drive by extending the 4kb reads with a sliding window cache.
That will help both drive efficiency, and also speed up the cases where
sub sequent boots differ just a little bit from the primed boot (often
the case with parallel init scripts). It should win you a few seconds
more in total, would be my guess.

I hope to be able to extend it to xfs and reiser in the very near future
as well, should not be hard to do.

-- 
Jens Axboe