Re: Route cache performance under stress

[Andi Kleen <ak@xxxxxxx>]

On Tue, Jun 10, 2003 at 06:23:38PM -0700, David S. Miller wrote:
>    From: Ralph Doncaster <ralph@xxxxxxxxx>
>    Date: Tue, 10 Jun 2003 21:17:28 -0400 (EDT)
> 
>    Aren't the read_lock_irqsave and restore expensive?
> 
> If x86 has an inefficient implementation, well... :-)

sti/cli is normally fast on x86, a bit slower on P3 core (a few cycles or so)
read_lock_irqsave does a pushfl though, that's rather slow on P4,
but still not that bad. read_lock_irq would be faster, but too risky 
here.

> 
> This can be done without locks, nobody has done the x86 implementation
> of that that's all.  I think the x86_64 folks did a lockless version,
> I know I did for sparc64 :)

2.5 i386 gettimeofday is lockless. But on UP it should not make any difference
anyways.

-Andi