On Thu, 2008-06-12 at 09:36 +0530, Aneesh Kumar K.V wrote:
> On Wed, Jun 11, 2008 at 12:07:49PM -0700, Andrew Morton wrote:
> > On Wed, 11 Jun 2008 20:38:45 +0530
> > "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx> wrote:
> The idea is to have ext3/4_writepages. In writepages start a transaction
> and iterate over the pages take the lock and do block allocation. With
> that change we should be able to not do block allocation in the
> page_mkwrite path. We may still want to do block reservation there.
>
> Something like.
>
> ext4_writepages()
> {
> journal_start()
> for_each_page()
Even with delayed allocation, the vast majority of the pages won't need
any allocations. You'll hit delalloc, do a big chunk with the journal
lock held and then do simple writepages that don't need anything
special.
I know the jbd journal_start is cheaper than the reiserfs one is, but it
might not perform well to hold it across the long writepages loop. At
least reiser saw a good boost when I stopped calling journal_begin in
writepage unless the page really needed allocations.
With the loop you have in mind, it is easy enough to back out and start
the transaction only when required.
-chris
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