Re: multi-queue scheduler update

[Davide Libenzi]

On Thursday 18 January 2001 17:33, Mike Kravetz wrote:
> On Fri, Jan 19, 2001 at 02:08:52AM +0100, Andi Kleen wrote:
> > On Thu, Jan 18, 2001 at 08:00:16PM -0500, Mark Hahn wrote:
> > > > >                            microseconds/yield
> > > > > # threads      2.2.16-22           2.4        2.4-multi-queue
> > > > > ------------   ---------         --------     ---------------
> > > > > 16               18.740            4.603         1.455
> > > >
> > > > I remeber the O(1) scheduler from Davide Libenzi was beating the
> > > > mainline O(N)
> > >
> > > isn't the normal case (as in "The Right Case to optimize")
> > > where there are close to zero runnable tasks?  what realistic/sane
> > > scenarios have very large numbers of spinning threads?  all server
> > > situations I can think of do not.  not volanomark -loopback, surely!
> >
> > I think the main point of Mike's patch is decreasing locking and cache
> > line bouncing overhead of multi cpu scheduling, not optimizing lots of
> > runnable tasks.
> >
> >
> > -Andi
>
> Andi is correct.  Although the results I posted may seem to indicate
> we are concentrating on high thread counts, this is really secondary
> to reducing lock contention within the scheduler.  A co-worker down
> the hall just ran pgbench (a postgresql db) benchmark and saw
> contention on the runqueue lock at 57%.  Now, I know nothing about this
> benchmark, but it will be interesting to see what happens after
> applying my patch.

Yep, the patch work in a different way and if these are the numbers it seems 
to be interesting.
Could You post results for a fewer number of tasks ?
I mean what is the performance loss for 1,2,..,5 tasks ?

To test You can use lmbench ( I don't remember the link ) and I should have 
the program I've used to test my patch somewhere.

- Davide