>
> However I'm not sure 256 is a good number. It seems a bit too high.
it's 256 context switches... if you care about context switch cycles
you'll do many, and 256 isn't a lot ;)
(remember that this is after 5 *consecutive* fpu uses, not just 5 uses
total, to you're really a heavy fpu user if you hit that)
>
> > Index: linux-2.6.17-sleazyfpu/arch/x86_64/kernel/process.c
> > ===================================================================
> > --- linux-2.6.17-sleazyfpu.orig/arch/x86_64/kernel/process.c
> > +++ linux-2.6.17-sleazyfpu/arch/x86_64/kernel/process.c
> > @@ -515,6 +515,10 @@ __switch_to(struct task_struct *prev_p,
> > int cpu = smp_processor_id();
> > struct tss_struct *tss = &per_cpu(init_tss, cpu);
> >
> > + /* we're going to use this soon, after a few expensive things */
> > + if (next_p->fpu_counter>5)
> > + prefetch(&next->i387.fxsave);
>
> Did you measure this prefetch makes a difference? I would expect it to
> be too soon to be really worth while (normally you need hundreds of
> instructions for them to make sense and that's probably not the case here)
s/instructions/cycles/
well there are 4 segment loads, a few msr accesses, a few PDA writes and
optionally even the fxsave of the old task inbetween the prefetch and
the use of the memory; those do add up *bigtime*...
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
