On Wed, Mar 04, 2009 at 03:04:11PM +1100, Benjamin Herrenschmidt wrote: > On Thu, 2009-02-19 at 18:21 +0100, Nick Piggin wrote: > > OK, here is this patch again. You didn't think I'd let a 2% performance > > improvement be forgotten? :) > > > > Anyway, patch won't work well on architecture without lwsync, but I won't > > bother fixing that kind of thing and making it merge worthy until you > > guys say something positive about it. > > > > 20 runs of tbench on the G5 > > > > unpatched AVG=920.37 STD=2.36 > > patched AVG=938.89 STD=3.33 > > > > (throughput in MB/s) This is a 1.9% throughput increase. > > Definitely worth it believe. We could use a macro that uses michael new > improvements on the CPU features code pathing so that the isync gets > changed to lwsync on some CPUs based on the availability of it.
OK. I guess the interesting part about this is that I can't find any IBM documentation for lwsync capable CPUs that suggest using this pattern for acquire locking. It would be interesting to know whether it helps other CPUs... _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
