Re: ext3 IO latency measurements (was: Linux 2.6.29)

Linus Torvalds
2009-03-27T22:19:44Z

On Fri, 27 Mar 2009, Jan Kara wrote:
>
> Doable but not fairly simple ;) Firstly you have to restart a transaction
> when you've used up all the credits you originally started with (easy),
> secondly ext3 uses lock order PageLock -> "transaction start" which is
> unusable for the scheme you suggest. So we'd have to revert that - which
> needs larger audit of our locking scheme and that's probably the reason
> why noone has done it yet.

It's also not clear that ext3 can really do much better than the regular
generic_writepages() logic. I mean, seriously, what's there to improve on?
The transaction code is all normally totally pointless, and I merged the
patch that avoids it when not necessary.

It might be different if more people used "data=journal", but I don't
doubt that is very common. For data=writeback and data=ordered, I bet
generic_writepages() is as good as anything ext3-specific could be.

Linus