Re: Nick's vfs-scalability patches ported to 2.6.33-rt

[john stultz <johnstul@us.ibm.com>]

On Thu, 2010-03-04 at 14:33 +1100, Nick Piggin wrote:
> On Wed, Mar 03, 2010 at 03:31:30PM -0800, john stultz wrote:
> > On Fri, 2010-02-26 at 17:01 +1100, Nick Piggin wrote:
> > > On Thu, Feb 25, 2010 at 09:53:28PM -0800, john stultz wrote:
> > > > Hey Thomas, Nick,
> > > > 	I just wanted to let you know I've just finished forward porting Nick's
> > > > patches to 2.6.33-rc8-rt2.  Luckily my forward port of Nick's patches to
> > > > 2.6.33 applies on top of the -rt tree without any collisions, and I've
> > > > added a handful of maybe sketchy fixups to get it working with -rt.
> > > > 
> > > > You can find the patchset here:
> > > > http://sr71.net/~jstultz/dbench-scalability/patches/2.6.33-rc8-rt2/vfs-scale.33-rt.tar.bz2
> > > > 
> > > > Here's a chart showing how much these patches help dbench numbers on
> > > > ramfs:
> > > > http://sr71.net/~jstultz/dbench-scalability/graphs/2.6.33/ramfs-dbench.png
> > > > 
> > > > I've not done any serious stress testing with the patchset yet, but
> > > > wanted to post it for your review.
> > > > 
> > > > Nick: I'd appreciate any feedback as to if any of my forward porting has
> > > > gone awry. I'm still very green with respect to the vfs, so I don't
> > > > doubt there are some issues hiding here.
> > > 
> > > BTW there are a few issues Al pointed out. We have to synchronize RCU
> > > after unregistering a filesystem so d_ops/i_ops doesn't go away, and
> > > mntput can sleep so we can't do it under RCU read lock.
> > 
> > Does the following address this issue properly?
> 
> As far as I could tell, yes that should solve the code reference
> problem. I don't see a problem with synchronizing RCU here.

Good to hear! Thanks for the review Nick!


Thomas:  I ran a number of kernel-bench and dbench stress tests on this
today and I've not seen any issues, so unless Nick has other issues, I
think it should be ok to pull into -rt.

You can grab the full patchset that builds ontop of 2.6.33-rt4 here:
http://sr71.net/~jstultz/dbench-scalability/patches/2.6.33-rt4/vfs-scale.33-rt.tar.bz2

thanks
-john