Re: [PATCH] Read-Copy Update 2.5.34

[Dipankar Sarma <dipankar@in.ibm.com>]

On Wed, Sep 11, 2002 at 10:03:28AM -0400, Robert Love wrote:
> On Wed, 2002-09-11 at 08:20, Dipankar Sarma wrote:
> 
> > 			vanilla-2.5.34	rcu_poll-2.5.34
> > 			--------------  ---------------
> > 80 , 40 , 		1.593		1.569
> > 112 , 40 , 		1.544		1.554
> > 144 , 40 , 		1.595		1.552
> > 176 , 40 , 		1.568		1.605
> > 198 , 40 , 		1.562		1.577
> > 230 , 40 , 		1.563		1.583
> > 244 , 40 , 		1.671		1.638
> > 
> > Not sure how reliable these numbers are.
> 
> And how bad is the performance drop from 2.5.34-preempt to
> 2.5.34-preempt-rcu?
> 
> I am glad you guys support kernel preemption (not that you have a chance
> at this point) but I hope it was not an afterthought.

Hi Robert,

Sorry, I should have been more careful labelling them - those are 2.5.34-preempt
vs 2.5.34-preempt-rcu numbers. I did them first because rcu-poll-preempt
kernel has a conditinal branch in fast path and hence more interesting. 
I will publish the vanilla vs rcu_poll reflex numbers in a few minutes 
from now.

The preemption support have been in RCU for a very long time. IIRC, I added
it in around 2.5.14.

See http://marc.theaimsgroup.com/?l=linux-kernel&m=102084967517192&w=2

Our OLS paper and presentation too deals with preemption -

http://www.rdrop.com/users/paulmck/rclock/rcu.2002.07.08.pdf
http://www.rdrop.com/users/paulmck/rclock/rclock.OLS.2002.07.08a.pdf

Thanks
-- 
Dipankar Sarma  <dipankar@in.ibm.com> http://lse.sourceforge.net
Linux Technology Center, IBM Software Lab, Bangalore, India.