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Date: Wed, 25 Jan 2023 16:09:35 +0000
From: Qais Yousef <qyousef@...alina.io>
To: Vincent Guittot <vincent.guittot@...aro.org>
Cc: Kajetan Puchalski <kajetan.puchalski@....com>, mingo@...nel.org,
peterz@...radead.org, dietmar.eggemann@....com, rafael@...nel.org,
viresh.kumar@...aro.org, vschneid@...hat.com,
linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
lukasz.luba@....com, wvw@...gle.com, xuewen.yan94@...il.com,
han.lin@...iatek.com, Jonathan.JMChen@...iatek.com
Subject: Re: [PATCH v4] sched/fair: unlink misfit task from cpu overutilized
On 01/25/23 09:37, Vincent Guittot wrote:
> On Wed, 25 Jan 2023 at 02:46, Kajetan Puchalski
> <kajetan.puchalski@....com> wrote:
> >
> > Hi,
> >
> > > By taking into account uclamp_min, the 1:1 relation between task misfit
> > > and cpu overutilized is no more true as a task with a small util_avg may
> > > not fit a high capacity cpu because of uclamp_min constraint.
> > >
> > > Add a new state in util_fits_cpu() to reflect the case that task would fit
> > > a CPU except for the uclamp_min hint which is a performance requirement.
> > >
> > > Use -1 to reflect that a CPU doesn't fit only because of uclamp_min so we
> > > can use this new value to take additional action to select the best CPU
> > > that doesn't match uclamp_min hint.
> > >
> >
> > Just wanted to include some more test data here to flag potential issues
> > with how all these changes use thermal pressure in the scheduler.
> >
> > For the tables below, 'baseline' is pre the already merged "uclamp fits
> > capacity" patchset.
> > 'baseline_ufc' is the current mainline with said patchset applied.
> > The 'no_thermal' variants are variants with thermal handling taken out
> > of util_fits_cpu akin to the v1 variant of the patchset.
> > The 'patched' variants are the above but with the v4 of the 'unlink misfit
> > task' patch applied as well.
> >
> > Geekbench 5:
> >
> > +-----------------+-------------------------+--------+-----------+
> > | metric | kernel | value | perc_diff |
> > +-----------------+-------------------------+--------+-----------+
> > | multicore_score | baseline | 2765.4 | 0.0% |
> > | multicore_score | baseline_ufc | 2704.3 | -2.21% | <-- mainline score regression
> > | multicore_score | baseline_ufc_no_thermal | 2870.8 | 3.81% | <-- ~170 pts better without thermal
> > | multicore_score | ufc_patched_v4 | 2839.8 | 2.69% | <-- no more regression but worse than above
> > | multicore_score | ufc_patched_no_thermal | 2891.0 | 4.54% | <-- best score
> > +-----------------+-------------------------+--------+-----------+
> >
> > +--------------+--------+-------------------------+--------+-----------+
> > | chan_name | metric | kernel | value | perc_diff |
> > +--------------+--------+-------------------------+--------+-----------+
> > | total_power | gmean | baseline | 2664.0 | 0.0% |
> > | total_power | gmean | baseline_ufc | 2621.5 | -1.6% |
> > | total_power | gmean | baseline_ufc_no_thermal | 2710.0 | 1.73% |
> > | total_power | gmean | ufc_patched_v4 | 2729.0 | 2.44% |
> > | total_power | gmean | ufc_patched_no_thermal | 2778.1 | 4.28% |
> > +--------------+--------+-------------------------+--------+-----------+
> >
> > (Jankbench scores show more or less no change, Jankbench power below)
> >
> > +--------------+--------+------------------------------+-------+-----------+
> > | chan_name | metric | kernel | value | perc_diff |
> > +--------------+--------+------------------------------+-------+-----------+
> > | total_power | gmean | baseline_60hz | 135.9 | 0.0% |
> > | total_power | gmean | baseline_ufc_60hz | 155.7 | 14.61% | <-- mainline power usage regression
> > | total_power | gmean | baseline_ufc_no_thermal_60hz | 134.5 | -1.01% | <-- no more regression without the thermal bit
> > | total_power | gmean | ufc_patched_v4_60hz | 131.4 | -3.26% | <-- no more regression with the patch either
> > | total_power | gmean | ufc_patched_no_thermal_60hz | 140.4 | 3.37% | <-- both combined increase power usage
> > +--------------+--------+------------------------------+-------+-----------+
> >
> > Specifically the swing of +15% power to -1% power by taking out thermal
> > handling from util_fits_cpu on the original patchset is noteworthy. It
> > shows that there's some subtle thermal-related interaction there taking
> > place that can have adverse effects on power usage.
> >
> > Even more interestingly, the 'unlink misfit task' patch appears to be
> > preventing said interaction from happening down the line as it has a
> > similar effect to that of just taking out the thermal bits.
> >
> > My only concern here is that without taking a closer look at the thermal
> > parts this power issue shown above could easily accidentally be
> > reintroduced at some point in the future.
>
> Yes, the handling of thermal pressure needs some closer look. It has
> been agreed to keep the current behavior for now and have a closer
> look on thermal pressure as a next step. And your results for
> ufc_patched_v4_* provide some reasonably good perf and power figures.
Note that the GB perf improvements can be pure accidental because now some UI
tasks that are boosted end up spending more time on medium and big cores and
increasing the higher frequency residency there.
For example looking at my old result against v1 of my patches I can see for the
big cores the top frequency residency moves from 11.74% (mainline-sh 5.10
kernel) to 18.98%. I see tasks with uclamp_min value of 512 in the system.
On medium it improves by ~2% (30% to 32%).
Note that userspace now can dynamically set uclamp_min values and we don't
understand how this interaction goes.
I luckily had some old data of the results I collected when I ran v1 to
hopefully help demonstrate how uclamp_min behaves:
Kernel B here is: Stock android12-5.10 without out of tree sched changes.
Kernel C: Kernel B + v1 of my patches.
(Kernel A was the stock kernel in my experiments if you're wondering)
The first two tables show uclamp_min values per cpu. Note how with my fixes now
512 values are more dominant on cpus 4-7 (75% is 512).
The second set of tables shows the non zero uclamp_min values per task. Note
how on Kernel B the max is 398 for many tasks. On Pixel 6 the capacities are:
L: 160
M: 498
B: 1024
498 * 0.8 = 398. So they get capped to 80% which is the migration margin
I resolved the relationship with.
Also note how AyncTask get boosted to 512 on Kernel C while they don't seem to
be boosted on Kernel B. Not sure why. I assume something with the cgroup
settings changes for some reason. Userspace configuration is not tuned to this
behavior anyway so I'm not sure what we see is optimal. So I'd take results
generally with a grain of salt. Note the 512 boost will result in these tasks
preferring big cores more to honour uclamp_min.
Also note how RenderThread and hwuiTask have big standard deviation as they are
dynamically adjusted. RenderThread 50% goes from 442 to 496; which is near the
top boundary of the medium core. Last set of tables show the count for how many
each value was seen for RenderThread for each kernel.
Overall this demonstrates there's a complex set of interactions going on. And
generally geekbench is not a workload that I'd expect to benefit from uclamp
and saying that we improved/regressed can be misleading. I can't say for sure,
but it seems to benefit from few happy accidents. We need to look at this in
the light of how uclamp_min is being used by userspace.
FWIW I'll be backporting these patches to GKI and will run another detailed
analysis. For now I think what we have makes sense and is a good improvement.
(I'm still testing v4 with my unit test - need a bit more time as I'm trying to
improve my unit test too)
--->8---
Kernel B uclamp CFS
count mean std min 25% 50% 75% max
cpu
0 87542.0 0.172397 7.836326 0.0 0.0 0.0 0.0 512.0
1 87829.0 0.383404 11.910648 0.0 0.0 0.0 0.0 512.0
2 81713.0 0.371801 11.621681 0.0 0.0 0.0 0.0 512.0
3 85040.0 0.334113 11.160260 0.0 0.0 0.0 0.0 512.0
4 93270.0 1.032915 20.262032 0.0 0.0 0.0 0.0 512.0
5 93820.0 1.057003 20.036322 0.0 0.0 0.0 0.0 512.0
6 71159.0 4.901868 46.765630 0.0 0.0 0.0 0.0 512.0
7 78797.0 4.414445 43.265857 0.0 0.0 0.0 0.0 512.0
Kernel C uclamp CFS
count mean std min 25% 50% 75% max
cpu
0 78514.0 55.845161 159.535262 0.0 0.0 0.0 0.0 512.0
1 78231.0 73.549296 179.461818 0.0 0.0 0.0 0.0 512.0
2 73310.0 80.742873 186.373848 0.0 0.0 0.0 0.0 512.0
3 69998.0 86.269151 191.512815 0.0 0.0 0.0 0.0 512.0
4 86887.0 169.776802 240.719169 0.0 0.0 0.0 512.0 512.0
5 87763.0 176.961875 243.162097 0.0 0.0 0.0 512.0 512.0
6 83600.0 257.773505 255.694248 0.0 0.0 506.0 512.0 512.0
7 74770.0 217.606380 252.568571 0.0 0.0 0.0 512.0 512.0
Kernel B uclamp SE
count mean std min 25% 50% 75% max
comm
AudioThread 8.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
Chrome_ChildIOT 35.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
Chrome_DevTools 2.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
Chrome_IOThread 132.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
Chrome_InProcGp 74.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
Chrome_ProcessL 22.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
CleanupReferenc 3.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
CookieMonsterBa 2.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
CookieMonsterCl 4.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
CrAsyncTask #1 3.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
MemoryInfra 5.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
NetworkService 20.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
RenderThread 773.0 350.175938 181.779995 6.0 225.0 448.0 512.0 512.0
SharedPreferenc 1.0 398.000000 NaN 398.0 398.0 398.0 398.0 398.0
Thread-2 1.0 398.000000 NaN 398.0 398.0 398.0 398.0 398.0
Thread-3 5.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
ThreadPoolForeg 156.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
ThreadPoolServi 47.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
ThreadPoolSingl 13.0 415.538462 42.810854 398.0 398.0 398.0 398.0 512.0
VizWebView 128.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
droid.launcher3 10.0 512.000000 0.000000 512.0 512.0 512.0 512.0 512.0
getprop 21.0 512.000000 0.000000 512.0 512.0 512.0 512.0 512.0
hwuiTask0 219.0 310.917808 190.832514 6.0 90.0 307.0 512.0 512.0
hwuiTask1 230.0 331.786957 186.994297 6.0 225.0 307.0 512.0 512.0
labs.geekbench5 1037.0 344.688525 180.838188 6.0 175.0 398.0 512.0 512.0
ll.splashscreen 99.0 457.060606 106.420692 253.0 512.0 512.0 512.0 512.0
mali-cmar-backe 17.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
mali-mem-purge 40.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
mali-utility-wo 18.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
ndroid.systemui 88.0 197.022727 197.388407 31.0 52.0 52.0 512.0 512.0
queued-work-loo 5.0 398.000000 0.000000 398.0 398.0 398.0 398.0 398.0
sh 7.0 512.000000 0.000000 512.0 512.0 512.0 512.0 512.0
Kernel C uclamp SE
count mean std min 25% 50% 75% max
comm
AsyncTask #1 128468.0 512.000000 0.000000 512.0 512.00 512.0 512.0 512.0
AudioThread 8.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
Chrome_ChildIOT 35.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
Chrome_DevTools 2.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
Chrome_IOThread 154.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
Chrome_InProcGp 91.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
Chrome_ProcessL 18.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
CleanupReferenc 3.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
CookieMonsterBa 2.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
CookieMonsterCl 5.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
CrAsyncTask #1 3.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
MemoryInfra 4.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
NetworkService 18.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
RenderThread 965.0 380.451813 172.243131 6.0 235.00 496.0 512.0 512.0
SharedPreferenc 1.0 512.000000 NaN 512.0 512.00 512.0 512.0 512.0
Thread-2 1.0 436.000000 NaN 436.0 436.00 436.0 436.0 436.0
Thread-3 5.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
ThreadPoolForeg 161.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
ThreadPoolServi 38.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
ThreadPoolSingl 13.0 447.692308 28.540569 436.0 436.00 436.0 436.0 512.0
VizWebView 115.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
droid.launcher3 12.0 512.000000 0.000000 512.0 512.00 512.0 512.0 512.0
getprop 31.0 512.000000 0.000000 512.0 512.00 512.0 512.0 512.0
hwuiTask0 249.0 368.489960 174.171868 9.0 169.00 496.0 512.0 512.0
hwuiTask1 254.0 354.704724 179.083049 6.0 169.00 458.0 512.0 512.0
labs.geekbench5 1008.0 361.363095 181.320417 6.0 201.25 436.0 512.0 512.0
ll.splashscreen 73.0 422.493151 83.830206 283.0 446.00 446.0 458.0 512.0
mali-cmar-backe 21.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
mali-mem-purge 35.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
mali-utility-wo 17.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
ndroid.systemui 201.0 290.731343 195.719308 51.0 109.00 140.0 512.0 512.0
queued-work-loo 7.0 436.000000 0.000000 436.0 436.00 436.0 436.0 436.0
sh 21.0 512.000000 0.000000 512.0 512.00 512.0 512.0 512.0
Kernel B RenderThread
512 361
253 59
307 40
84 39
264 37
52 36
225 30
16 28
398 21
472 19
448 13
43 5
216 5
375 5
138 4
87 4
143 4
112 4
501 4
21 4
190 4
6 4
67 4
25 4
175 4
347 3
13 3
126 3
93 3
103 3
129 3
100 2
78 2
413 2
97 2
242 1
75 1
31 1
115 1
81 1
Kernel C RenderThread
512 393
506 75
496 75
169 52
321 46
104 33
109 31
283 30
9 21
436 21
446 17
92 17
231 16
458 15
325 13
140 11
13 8
19 8
358 6
276 6
50 5
237 5
70 5
224 4
47 4
374 4
361 4
415 3
99 3
82 3
235 3
44 3
249 3
6 3
190 3
507 3
93 3
22 2
31 2
347 2
75 2
463 1
51 1
--->8---
Cheers
--
Qais Yousef
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