Hi Phil, On Thu, 29 Aug 2019 at 21:23, Phil Auld <[email protected]> wrote: > > On Thu, Aug 01, 2019 at 04:40:16PM +0200 Vincent Guittot wrote: > > Several wrong task placement have been raised with the current load
> > > > -- > > 2.7.4 > > > > I keep expecting a v3 so I have not dug into all the patches in detail. > However, I've v3 is under preparation > been working with them from Vincent's tree while they were under development > so I thought > I'd add some results. Yes. thanks for your help. > > The workload is a test our perf team came up with to illustrate the issues we > were seeing > with imbalance in the presence of group scheduling. > > On a 4-numa X 20 cpu system (smt on) we run a 76 thread lu.C benchmark from > the NAS Parallel > suite. And at the same time run 2 stress cpu burn processes. The GROUP test > puts the > benchmark and the stress processes each in its own cgroup. The NORMAL case > puts them all > in the first cgroup. The results show first the average number of threads of > each type > running on each of the numa nodes based on sampling taken during the run. > This is followed > by the lu.C benchmark results. There are 3 runs of GROUP and 2 runs of NORMAL > shown. > > Before (linux-5.3-rc1+ @ a1dc0446d649) > > lu.C.x_76_GROUP_1.stress.ps.numa.hist Average 0.00 1.00 1.00 > lu.C.x_76_GROUP_2.stress.ps.numa.hist Average 0.00 1.00 1.00 > lu.C.x_76_GROUP_3.stress.ps.numa.hist Average 0.00 1.00 1.00 > lu.C.x_76_NORMAL_1.stress.ps.numa.hist Average 1.15 0.23 0.00 0.62 > lu.C.x_76_NORMAL_2.stress.ps.numa.hist Average 1.67 0.00 0.00 0.33 > > lu.C.x_76_GROUP_1.ps.numa.hist Average 30.45 6.95 4.52 34.08 > lu.C.x_76_GROUP_2.ps.numa.hist Average 32.33 8.94 9.21 25.52 > lu.C.x_76_GROUP_3.ps.numa.hist Average 30.45 8.91 12.09 24.55 > lu.C.x_76_NORMAL_1.ps.numa.hist Average 18.54 19.23 19.69 18.54 > lu.C.x_76_NORMAL_2.ps.numa.hist Average 17.25 19.83 20.00 18.92 > > ============76_GROUP========Mop/s=================================== > min q1 median q3 max > 2119.92 2418.1 2716.28 3147.82 3579.36 > ============76_GROUP========time==================================== > min q1 median q3 max > 569.65 660.155 750.66 856.245 961.83 > ============76_NORMAL========Mop/s=================================== > min q1 median q3 max > 30424.5 31486.4 31486.4 31486.4 32548.4 > ============76_NORMAL========time==================================== > min q1 median q3 max > 62.65 64.835 64.835 64.835 67.02 > > > After (linux-5.3-rc1+ @ a1dc0446d649 + this v2 series pulled from > Vincent's git on ~8/15) > > lu.C.x_76_GROUP_1.stress.ps.numa.hist Average 0.36 1.00 0.64 > lu.C.x_76_GROUP_2.stress.ps.numa.hist Average 1.00 1.00 > lu.C.x_76_GROUP_3.stress.ps.numa.hist Average 1.00 1.00 > lu.C.x_76_NORMAL_1.stress.ps.numa.hist Average 0.23 0.15 0.31 1.31 > lu.C.x_76_NORMAL_2.stress.ps.numa.hist Average 1.00 0.00 0.00 1.00 > > lu.C.x_76_GROUP_1.ps.numa.hist Average 18.91 18.36 18.91 19.82 > lu.C.x_76_GROUP_2.ps.numa.hist Average 18.36 18.00 19.91 19.73 > lu.C.x_76_GROUP_3.ps.numa.hist Average 18.17 18.42 19.25 20.17 > lu.C.x_76_NORMAL_1.ps.numa.hist Average 19.08 20.00 18.62 18.31 > lu.C.x_76_NORMAL_2.ps.numa.hist Average 18.09 19.91 19.18 18.82 > > ============76_GROUP========Mop/s=================================== > min q1 median q3 max > 32304.1 33176 34047.9 34166.8 34285.7 > ============76_GROUP========time==================================== > min q1 median q3 max > 59.47 59.68 59.89 61.505 63.12 > ============76_NORMAL========Mop/s=================================== > min q1 median q3 max > 29825.5 32454 32454 32454 35082.5 > ============76_NORMAL========time==================================== > min q1 median q3 max > 58.12 63.24 63.24 63.24 68.36 > > > I had initially tracked this down to two issues. The first was picking the > wrong > group in find_busiest_group due to using the average load. The second was in > fix_small_imbalance(). The "load" of the lu.C tasks was so low it often failed > to move anything even when it did find a group that was overloaded (nr_running > > width). I have two small patches which fix this but since Vincent was > > embarking > on a re-work which also addressed this I dropped them. > > We've also run a series of performance tests we use to check for regressions > and > did not find any bad results on our workloads and systems. > > So... > > Tested-by: Phil Auld <[email protected]> Thanks for testing Vincent > > > Cheers, > Phil > --
