On Mon, Aug 06 2007, Nick Piggin wrote:
> > > What CPU did you get these numbers on? Do the indirect calls hurt much
> > > on those without an indirect predictor? (I'll try running some tests).
> >
> > it was on an older Athlon64 X2. I never saw indirect calls really
> > hurting on modern x86 CPUs - dont both CPU makers optimize them pretty
> > efficiently? (as long as the target function is always the same - which
> > it is here.)
>
> I think a lot of CPUs do. I think ia64 does not. It predicts
> based on the contents of a branch target register which has to
> be loaded I presume before instructoin fetch reaches the branch.
> I don't know if this would hurt or not.
Testing on ia64 showed that the indirect calls in the io scheduler hurt
quite a bit, so I'd be surprised if the impact here wasn't an issue
there.
--
Jens Axboe
-
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]
