On Fri, Aug 19, 2011 at 10:14:09AM -0400, Vivek Goyal wrote: > On Thu, Aug 18, 2011 at 02:03:56PM -0700, Andi Kleen wrote: > > > > >Is the performance gain because of this one less dereference really > > >substantial. > > Yes it is measurable on a large macro benchmark. > > > > The gain is from doing the prefetch early enough, and that needs the > > additional pointer. > > So it gives you extra .3% (as mentioned in your first mail). IMHO, for > .3% we should not cache extra request queue pointer. Note this is on a benchmark which is primarily userland. Kernel is only a small part, so it's a much higher percentage for the kernel time. Also on that large benchmark it's hard to any improvement at all, and this isn't even a particularly ugly or intrusive change. Not sure why you're against it. Cache optimizations are important. -Andi -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
