Re: [Ext2-devel] [RFC] Adding multiple block allocation

[Suparna Bhattacharya <suparna@in.ibm.com>]

On Sat, Apr 30, 2005 at 11:07:53AM -0700, Mingming Cao wrote:
> On Sat, 2005-04-30 at 22:41 +0530, Suparna Bhattacharya wrote:
> > On Sat, Apr 30, 2005 at 09:40:43PM +0530, Suparna Bhattacharya wrote:
> > > On Fri, Apr 29, 2005 at 04:22:59PM -0700, Mingming Cao wrote:
> > > > On Fri, 2005-04-29 at 11:45 -0700, Badari Pulavarty wrote:
> > > > > I touch tested your patch earlier and seems to work fine. Lets integrate
> > > > > Mingming's getblocks() patches with this and see if we get any benifit
> > > > > from the whole effort.
> > > > > 
> > > > 
> > > > I tried Suparna's mpage_writepages_getblocks patch with my
> > > > ext3_get_blocks patch, seems to work fine,  except that still only one
> > > > block is allocated at a time. I got a little confused.... 
> > > > 
> > > > I did not see any delayed allocation code in your patch, I assume you
> > > > have to update ext3_prepare_write to not call ext3_get_block, so that
> > > > block allocation will be defered at ext3_writepages time. So without the
> > > > delayed allocation part, the get_blocks in mpage_writepages is doing
> > > > multiple blocks look up only, right?
> > > 
> > > That's right - so you could try it with mmapped writes (which don't
> > > go through a prepare write) or with Badari's patch to not call
> > > ext3_get_block in prepare write.
> > 
> > BTW, I hope you are running with NOBH.
> 
> No, it was not run with NOBH. Why we need to turn on nobh here?

If the page has buffers, then get_blocks won't be invoked -- it either
finds all the buffers in a page to be mapped contiguous, in which case
it can directly issue the IO or enters the confused case where it goes
through block_write_full_page.

> 
> There are some issue running fsx tests with both patches, w/o direct io
> option. I will spend more time on this next week.

OK, I can take a look at the fsx logs, just in case it is similar to
something I've seen before.

Regards
Suparna

-- 
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Lab, India