On Tue, Jun 24, 2014 at 01:43:16PM -0700, Dave Hansen wrote: > On 06/23/2014 05:39 PM, Paul E. McKenney wrote: > > On Mon, Jun 23, 2014 at 05:20:30PM -0700, Dave Hansen wrote: > >> On 06/23/2014 05:15 PM, Paul E. McKenney wrote: > >>> Just out of curiosity, how many CPUs does your system have? 80? > >>> If 160, looks like something bad is happening at 80. > >> > >> 80 cores, 160 threads. >80 processes/threads is where we start using > >> the second thread on the cores. The tasks are also pinned to > >> hyperthread pairs, so they disturb each other, and the scheduler moves > >> them between threads on occasion which causes extra noise. > > > > OK, that could explain the near flattening of throughput near 80 > > processes. Is 3.16.0-rc1-pf2 with the two RCU patches? If so, is the > > new sysfs parameter at its default value? > > Here's 3.16-rc1 with e552592e applied and jiffies_till_sched_qs=12 vs. 3.15: > > > https://www.sr71.net/~dave/intel/bb.html?2=3.16.0-rc1-paultry2-jtsq12&1=3.15 > > 3.16-rc1 is actually in the lead up until the end when we're filling up > the hyperthreads. The same pattern holds when comparing > 3.16-rc1+e552592e to 3.16-rc1 with ac1bea8 reverted: > > > https://www.sr71.net/~dave/intel/bb.html?2=3.16.0-rc1-paultry2-jtsq12&1=3.16.0-rc1-wrevert > > So, the current situation is generally _better_ than 3.15, except during > the noisy ranges of the test where hyperthreading and the scheduler are > coming in to play.
Good to know that my intuition is not yet completely broken. ;-) > I made the mistake of doing all my spot-checks at > the 160-thread number, which honestly wasn't the best point to be > looking at. That would do it! ;-) > At this point, I'm satisfied with how e552592e is dealing with the > original regression. Thanks for all the prompt attention on this one, Paul. Glad it worked out, I have sent a pull request to Ingo to hopefully get this into 3.16. Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/