Re: ext3 writepages ?

[Badari Pulavarty <pbadari@us.ibm.com>]

On Wed, 2005-02-09 at 13:11, Sonny Rao wrote:
> On Tue, Feb 08, 2005 at 12:38:08AM -0500, Sonny Rao wrote:
> > On Mon, Feb 07, 2005 at 06:33:51PM -0700, Andreas Dilger wrote:
> > > On Feb 03, 2005  15:50 -0500, Sonny Rao wrote:
> > > > Well, from what I can tell, my patch doesn't seem to make much of a
> > > > difference in write throughput other than allowing multi-page bios to
> > > > be sent down and cutting down on buffer_head usage.
> > > 
> > > Even if it doesn't make a difference in performance, it might reduce the
> > > CPU usage.  Did you check that at all?
> > 
> > No I didn't, I'll check that out and post back.
> > 
> > Sonny
> 
> Ok, I take it back, on a raid device I saw a significant increase in
> throughput and approximately equal cpu utilization.   I was comparing
> the wrong data points before.. oops.
> 
> Sequential overwrite went from 75.6 MB/sec to 87.7 MB/sec both with an
> average CPU utilization of 73% for both.
> 
> So, I see a 16% improvement in throughput for this test case and a
> corresponding increase in efficiency. 
> 
> Although, after reading what SCT wrote about writepage and writepages
> needing to have a transaction handle, in some cases, that might  make
> the proper writepages code significantly more complex than my two-bit
> hack.  Still, I think it's worth it.

Yep. I hacked ext3_write_pages() to use mpage_writepages() as you did
(without modifying bufferheads stuff). With the limited testing I did,
I see much larger IO chunks and better throughput. So, I guess its
worth doing it - i am little worried about error handling though..

Lets handle one issue at a time. 

First fix writepages() without bufferhead changes ? Then handle
bufferheads ? I still can't figure out a way to workaround the
bufferheads especially for ordered writes.

Thanks,
Badari