On Tue, Sep 22, 2020 at 09:46:22PM -0400, Joel Fernandes wrote: > On Fri, Aug 28, 2020 at 11:29:27PM +0200, Peter Zijlstra wrote: > > > > > > This is still a horrible patch.. > > Hi Peter, > I wrote a new patch similar to this one and it fares much better in my tests, > it is based on Aaron's idea but I do the sync only during force-idle, and not > during enqueue. Also I yanked the whole 'core wide min_vruntime' crap. There > is a regressing test which improves quite a bit with my patch (results below): > > Aaron, Vineeth, Chris any other thoughts? This patch is based on Google's > 4.19 device kernel so will require some massaging to apply to mainline/v7 > series. I will provide an updated patch later based on v7 series. > > (Works only for SMT2, maybe we can generalize it more..) > --------8<----------- > > From: "Joel Fernandes (Google)" <[email protected]> > Subject: [PATCH] sched: Sync the min_vruntime of cores when the system enters > force-idle > > This patch provides a vruntime based way to compare two cfs task's priority, > be > it on the same cpu or different threads of the same core. > > It is based on Aaron Lu's patch with some important differences. Namely, > the vruntime is sync'ed only when the CPU goes into force-idle. Also I removed > the notion of core-wide min_vruntime. > > Also I don't care how long a cpu in a core is force idled, I do my sync > whenever the force idle starts essentially bringing both SMTs to a common time > base. After that point, selection can happen as usual. > > When running an Android audio test, with patch the perf sched latency output: > > ----------------------------------------------------------------------------------------------------------------- > Task | Runtime ms | Switches | Average delay ms | Maximum > delay ms | Maximum delay at | > ----------------------------------------------------------------------------------------------------------------- > FinalizerDaemon:(2) | 23.969 ms | 969 | avg: 0.504 ms | max: > 162.020 ms | max at: 1294.327339 s > HeapTaskDaemon:(3) | 2421.287 ms | 4733 | avg: 0.131 ms | max: > 96.229 ms | max at: 1302.343366 s > adbd:(3) | 6.101 ms | 79 | avg: 1.105 ms | max: > 84.923 ms | max at: 1294.431284 s > > Without this patch and with Aubrey's initial patch (in v5 series), the max > delay looks much better: > > ----------------------------------------------------------------------------------------------------------------- > Task | Runtime ms | Switches | Average delay ms | Maximum > delay ms | Maximum delay at | > ----------------------------------------------------------------------------------------------------------------- > HeapTaskDaemon:(2) | 2602.109 ms | 4025 | avg: 0.231 ms | max: > 19.152 ms | max at: 522.903934 s > surfaceflinger:7478 | 18.994 ms | 1206 | avg: 0.189 ms | max: > 17.375 ms | max at: 520.523061 s > ksoftirqd/3:30 | 0.093 ms | 5 | avg: 3.328 ms | max: > 16.567 ms | max at: 522.903871 s
I messed up the change log, just to clarify - the first result is without patch (bad) and the second result is with patch (good). thanks, - Joel
