Re: [rfc] lockless get_user_pages for dio (and more)

[Dave Kleikamp <shaggy@linux.vnet.ibm.com>]

On Wed, 2007-12-12 at 16:40 +1100, Nick Piggin wrote:
> On Wednesday 12 December 2007 16:11, Dave Kleikamp wrote:
> > On Wed, 2007-12-12 at 15:57 +1100, Nick Piggin wrote:

> > > Anyway, I am hoping that someone will one day and test if this and
> > > find it helps their workload, but on the other hand, if it doesn't
> > > help anyone then we don't have to worry about adding it to the
> > > kernel ;) I don't have any real setups that hammers DIO with threads.
> > > I'm guessing DB2 and/or Oracle does?
> >
> > I'll try to get someone to run a DB2 benchmark and see what it looks
> > like.
> 
> That would be great if you could.

We weren't able to get in any runs before the holidays, but we finally
have some good news from our performance team:

"To test the effects of the patch, an OLTP workload was run on an IBM
x3850 M2 server with 2 processors (quad-core Intel Xeon processors at
2.93 GHz) using IBM DB2 v9.5 running Linux 2.6.24rc7 kernel. Comparing
runs with and without the patch resulted in an overall performance
benefit of ~9.8%. Correspondingly, oprofiles showed that samples from
__up_read and __down_read routines that is seen during thread contention
for system resources was reduced from 2.8% down to .05%. Monitoring
the /proc/vmstat output from the patched run showed that the counter for
fast_gup contained a very high number while the fast_gup_slow value was
zero."

Great work, Nick!

Thanks,
Shaggy
-- 
David Kleikamp
IBM Linux Technology Center