Re: [RFC] Use RCU for tcp_ehash lookup

[Andi Kleen <ak@xxxxxxx>]

On Wed, Sep 01, 2004 at 05:06:41PM +0530, Srivatsa Vaddagiri wrote:
>                            |  2.6.8.1               | 2.6.8.1 + my patch
> -------------------------------------------------------------------------------
> Average cycles                     |                        |
> spent in                   |                        |
> __tcp_v4_lookup_established  |        2970.65               | 668.227
>                            | (~3.3 micro-seconds)   | (~0.74 microseconds)
> -------------------------------------------------------------------------------
> 
> This repesents improvement by a factor of 77.5%!

Nice.

> 
> 
> > 
> > And it should also fix the performance problems with
> > cat /proc/net/tcp on ppc64/ia64 for large hash tables because the rw locks 
> > are gone.
> 
> But spinlocks are in! Would that still improve the performance compared to rw 
> locks?  (See me earlier note where I have explained that lookup done for 
> /proc/net/tcp is _not_ lock-free yet).

Yes, spinlocks are much faster than rwlocks.

-Andi