Re: Severe I/O performance regression 2.6.6 to 2.6.7 or 2.6.8-rc3

[Marcelo Tosatti]

On Thu, Aug 05, 2004 at 01:46:15PM -0700, William Lee Irwin III wrote:
> William Lee Irwin III wrote:
> >> By any chance could you do binary search on the bk snapshots between
> >> 2.6.6 and 2.6.7?
> 
> On Thu, Aug 05, 2004 at 02:58:50PM -0500, Mr. Berkley Shands wrote:
> > the problem does not exist using 2.6.6-bk6, but exists on 2.6.6-bk7. 
> > -bk8 and -bk9 faile to build.
> > these are from patches-2.6.6-bk6 off snapshots/old and applied to a 
> > vanilla 2.6.6 kernel.
> 
> This is the closest it appears to be possible to narrow down where the
> regression happened.
> 
> Some form of changelogging to enumerate what the contents of the
> 2.6.6-bk6 -> 2.6.6-bk7 delta are and to reconstruct intermediate points
> between 2.6.6-bk6 and 2.6.6-bk7 is needed.

Indeed its nasty, the problem is there is no tagging in the main BK repository
representing the -bk tree's. It shouldnt be too hard to do something about 
this? I can't think of anything which could help...

> I have already tried to carry out various procedures to accomplish this
> for several other problem reports and/or issues and come have come away
> from the effort highly discouraged (having made zero progress) each time.

A quick look in bk6-bk7 reveals the regression is probably related 
to either the readahead changes or, less likely, the mm/vmscan.c 
changes.

I'm attaching a tarball with "readahead" and "vmscan", Mr. Berkley 
can you try reverting these ones at a time and repeating your tests?

Thanks!

Attachment: patches-bk6-bk7.tar.bz2
Description: BZip2 compressed data