On Thu, Feb 09, 2017 at 07:54:05PM +0100, Uladzislau Rezki wrote: > > Does this patch make an actual difference, if so how much and with > > what workload? > > > Yes, it does. I see a slight improvement when it comes to frame drops > (in my case drops per/two seconds). Basically a test case is left finger > swipe on the display (21 times, duration is 2 seconds + 1 second sleep > between iterations): > > 0 Framedrops: 7 5 > 1 Framedrops: 5 3 > 2 Framedrops: 8 5 > 3 Framedrops: 4 5 > 4 Framedrops: 3 3 > 5 Framedrops: 6 4 > 6 Framedrops: 3 2 > 7 Framedrops: 3 4 > 8 Framedrops: 5 3 > 9 Framedrops: 3 3 > 10 Framedrops: 7 4 > 11 Framedrops: 3 4 > 12 Framedrops: 3 3 > 13 Framedrops: 3 3 > 14 Framedrops: 3 5 > 15 Framedrops: 7 3 > 16 Framedrops: 5 3 > 17 Framedrops: 3 2 > 18 Framedrops: 5 3 > 19 Framedrops: 4 3 > 20 Framedrops: 3 2 > > max is 8 vs 5; min is 2 vs 3. > > As for applied load, it is not significant and i would say is "light".
So that is useful information that should have been in the Changelog. OK, can you respin this patch with adjusted Changelog and taking Mike's feedback? Also, I worry about the effects of this on !PREEMPT kernels, the first hunk (which explicitly states is about latency) should be under CONFIG_PREEMPT to match the similar case we already have in detach_tasks(). But your second hunk, which ignores the actual load of tasks in favour of just moving _something_ already, is utterly dangerous if not coupled with these two other conditions, so arguably that too should be under CONFIG_PREEMPT.
