On Mon, Mar 17, 2014 at 05:20:10PM -0700, Davidlohr Bueso wrote: > On Thu, 2013-12-19 at 11:51 -0800, tip-bot for Len Brown wrote: > > Commit-ID: 40e2d7f9b5dae048789c64672bf3027fbb663ffa > > Gitweb: http://git.kernel.org/tip/40e2d7f9b5dae048789c64672bf3027fbb663ffa > > Author: Len Brown <len.brown@xxxxxxxxx> > > AuthorDate: Wed, 18 Dec 2013 16:44:57 -0500 > > Committer: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx> > > CommitDate: Thu, 19 Dec 2013 11:47:39 -0800 > > > > x86 idle: Repair large-server 50-watt idle-power regression > > FYI this commit can cause some non trivial performance regressions for > larger core count systems. While not surprising because of the nature of > the change, having intel_idle do more cacheline invalidations, I still > wanted to let you guys know. For instance, on a 160 core Westmere > system, aim7 throughput can go down in a number of tests, anywhere from > -10% to -25%. > > I guess it comes down to one of those performance vs energy things. And > sure, max_cstate can be set to overcome this, but it's still something > that was previously taken for granted. -10% to -25% seems a lot for a single cacheline flush. Also I would expect the expected idle time to be very short while running aim7. So could it be the cacheflush is actually taking longer than the expected idle time? -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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