Re: [PATCH] [RFC] Optimize select/poll by putting small data sets on the stack

[Andi Kleen]

On Wednesday 04 January 2006 00:07, Eric Dumazet wrote:
> Eric Dumazet a Ãcrit :
> > Andi Kleen a Ãcrit :
> >> This is a RFC for now. I would be interested in testing
> >> feedback. Patch is for 2.6.15.
> >>
> >> Optimize select and poll by a using stack space for small fd sets
> >>
> >> This brings back an old optimization from Linux 2.0. Using
> >> the stack is faster than kmalloc. On a Intel P4 system
> >> it speeds up a select of a single pty fd by about 13%
> >> (~4000 cycles -> ~3500)
> >
> > Was this result on UP or SMP kernel ? Preempt or not ?
> >
> > I think we might play in do_pollfd() and use fget_light()/fput_light()
> > instead of fget()/fput() that are somewhat expensive because of atomic
> > inc/dec on SMP.
>
> Just for completeness I include this patch against 2.6.15

Looks like a good idea.

-Andi
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