Messages in this thread | | | Date | Sat, 28 Mar 2009 12:43:03 -0700 | From | Andrew Morton <> | Subject | Re: ext3 IO latency measurements (was: Linux 2.6.29) |
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On Fri, 27 Mar 2009 15:10:56 -0700 (PDT) Linus Torvalds <torvalds@linux-foundation.org> wrote:
> 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?
- opening a single transaction for many pages in the cases when a transaction _is_ needed.
- single large BIO versus zillions of single-page BIOs.
Relatively minor benefits, but it's a bit odd that we never got around to doing it.
It just got quite a bit harder to do, so I expect we won't be doing it.
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