On Fri, Mar 15, 2019 at 05:03:47PM +0100 Peter Zijlstra wrote: > On Fri, Mar 15, 2019 at 11:30:42AM -0400, Phil Auld wrote: > > > In my defense here, all the fair.c imbalance pct code also uses 100 :) > > Yes, I know, I hate on that too ;-) Just never got around to fixing > that. > > > > with the below: > > > > [ 117.235804] cfs_period_timer[cpu2]: period too short, scaling up (new > > cfs_period_us 2492, cfs_quota_us = 143554) > > [ 117.346807] cfs_period_timer[cpu2]: period too short, scaling up (new > > cfs_period_us 2862, cfs_quota_us = 164863) > > [ 117.470569] cfs_period_timer[cpu2]: period too short, scaling up (new > > cfs_period_us 3286, cfs_quota_us = 189335) > > [ 117.574883] cfs_period_timer[cpu2]: period too short, scaling up (new > > cfs_period_us 3774, cfs_quota_us = 217439) > > [ 117.652907] cfs_period_timer[cpu2]: period too short, scaling up (new > > cfs_period_us 4335, cfs_quota_us = 249716) > > [ 118.090535] cfs_period_timer[cpu2]: period too short, scaling up (new > > cfs_period_us 4978, cfs_quota_us = 286783) > > [ 122.098009] cfs_period_timer[cpu2]: period too short, scaling up (new > > cfs_period_us 5717, cfs_quota_us = 329352) > > [ 126.255209] cfs_period_timer[cpu2]: period too short, scaling up (new > > cfs_period_us 6566, cfs_quota_us = 378240) > > [ 126.358060] cfs_period_timer[cpu2]: period too short, scaling up (new > > cfs_period_us 7540, cfs_quota_us = 434385) > > [ 126.538358] cfs_period_timer[cpu9]: period too short, scaling up (new > > cfs_period_us 8660, cfs_quota_us = 498865) > > [ 126.614304] cfs_period_timer[cpu9]: period too short, scaling up (new > > cfs_period_us 9945, cfs_quota_us = 572915) > > [ 126.817085] cfs_period_timer[cpu9]: period too short, scaling up (new > > cfs_period_us 11422, cfs_quota_us = 657957) > > [ 127.352038] cfs_period_timer[cpu9]: period too short, scaling up (new > > cfs_period_us 13117, cfs_quota_us = 755623) > > [ 127.598043] cfs_period_timer[cpu9]: period too short, scaling up (new > > cfs_period_us 15064, cfs_quota_us = 867785) > > > > > > Plus on repeats I see an occasional > > > > [ 152.803384] sched_cfs_period_timer: 9 callbacks suppressed > > That should be fine, right? It's a fallback for an edge case and > shouldn't trigger too often anyway.
It doesn't hit the NMI, just takes a bit longer to get out. It is a little messier output, but as you say, it's a fallback. If you're okay with it do you want to just use your patch? Otherwise, I'm happy to do a fixup v2. > > >> I'll rework the maths in the averaged version and post v2 if that makes > >> sense. > > > > It may have the extra timer fetch, although maybe I could rework it so that > > it used the > > nsstart time the first time and did not need to do it twice in a row. I had > > originally > > reverted the hrtimer_forward_now() to hrtimer_forward() but put that back. > > Sure; but remember, simpler is often better, esp. for code that > typically 'never' runs. > > > Also, fwiw, this was reported earlier by Anton Blanchard in > > https://lkml.org/lkml/2018/12/3/1047 > > Bah, yes, I sometimes loose track of things :/ No worries. I just meant that to show I was not the only one with these low settings, and to give credit, or whatever :) Cheers, Phil --
