Messages in this thread | | | From | "Doug Smythies" <> | Subject | RE: [PATCH 0/6] cpuidle: menu: Fixes, optimizations and cleanups | Date | Mon, 8 Oct 2018 15:14:06 -0700 |
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On 2018.10.08 00:51 Rafael J. Wysocki wrote: > On Mon, Oct 8, 2018 at 8:02 AM Doug Smythies <dsmythies@telus.net> wrote: >> >> On 2018.10.03 23:56 Rafael J. Wysocki wrote: >>> On Tue, Oct 2, 2018 at 11:51 PM Rafael J. Wysocki <rjw@rjwysocki.net> wrote: >>>> >>>> Hi All, >>>> >>>> This series fixes a couple of issues with the menu governor, optimizes it >>>> somewhat and makes a couple of cleanups in it. Please refer to the >>>> patch changelogs for details. >>>> >>>> All of the changes in the series are straightforward in my view. The >>>> first two patches are fixes, the rest is optimizations and cleanups. >>> >>> I'm inclined to take this stuff in for 4.20 if nobody has problems >>> with it, so please have a look if you care (and you should, because >>> the code in question is run on all tickless systems out there). >> >> Hi Rafael, >> >> I did tests with kernel 4.19-rc6 as a baseline reference and then >> with 8 of your patches (&8patches in the graphs legend): >> >> cpuidle: menu: Replace data->predicted_us with local variable >> . as required to get this set of 6 to then apply. >> This set of 6 patches. >> cpuidle: poll_state: Revise loop termination condition >> >> Recall I also did some testing in late August [1], with >> a kernel that was just a few hundred commits before 4.19-rc1. >> The baseline is now way different. While I don't know why, >> I bisected the kernel and either made a mistake, or it was: >> >> first bad commit: [06e386a1db54ab6a671e103e929b590f7a88f0e3] >> Merge tag 'fbdev-v4.19' of https://github.com/bzolnier/linux >> >> Anyway, and for reference, included on some of the graphs >> is the old data from late August (legend name "4.18+3rjw >> (Aug test)") >> >> Test 1: A Thomas Ilsche type "powernightmare" test: >> (forever ((10 times - variable usec sleep) 0.999 seconds sleep) X 40 staggered threads. >> Where the "variable" was from 0.05 to 5 in steps of 0.05, for the first ~200 minutes of the test. >> (note: overheads mean that actual loop times are quite different.) >> And then from 5 to 50 in steps of 1, for the remaining 100 minutes of the test. >> (Shortened by 900 minutes from the way the test was done in August.) >> Each step ran for 2 minutes. The system was idle for 1 minute at the start, and a few >> minutes at the end of the graphs. >> >> The power and idle statistics graphs are here: >> http://fast.smythies.com/linux-pm/k419/k419-pn-sweep-rjw.htm >> >> Observations: >> >> While the graphs are pretty and such, the only significant >> difference is the idle state 0 percentages go down a lot >> with the 8 patches. However the number of idle state 0 >> entries per minute goes up. To present the same information >> in a different way a trace was done (at 9 Gigabytes in >> 2 minutes): > > The difference in the idle state 0 usage is a consequence of the "poll > idle" patch and is expected. > >> &8patches >> Idle State 0: Total Entries: 10091412 : time (seconds): 49.447025 >> Idle State 1: Total Entries: 49332297 : time (seconds): 375.943064 >> Idle State 2: Total Entries: 311810 : time (seconds): 2.626403 >> >> k4.19-rc6 >> Idle State 0: Total Entries: 9162465 : time (seconds): 70.650566 >> Idle State 1: Total Entries: 47592671 : time (seconds): 373.625083 >> Idle State 2: Total Entries: 266212 : time (seconds): 2.278159 >> >> Conclusions: Behaves as expected. > > Right. :-)
>> Test 2: pipe test 2 CPUs, one core. CPU test: >> >> The average loop times graph is here: >> http://fast.smythies.com/linux-pm/k419/k419-rjw-pipe-1core.png >> >> The power and idle statistics graphs are here: >> http://fast.smythies.com/linux-pm/k419/k419-rjw-pipe-1core.htm >> >> Conclusions: >> >> Better performance at the cost of more power with >> the patch set, but late August had both better performance >> and less power. >> >> Overall idle entries and exits are about the same, but way >> way more idle state 0 entries and exits with the patch set. > >Same as above (and expected too).
I Disagree. The significant transfer of idle entries from idle state 1 with kernel 4.19-rc6 to idle state 0 with the additional 8 patch set is virtually entirely due to this patch:
"[PATCH 2/6] cpuidle: menu: Compute first_idx when latency_req is known"
As far as I can determine from all of this data, in particular the histogram data below, it seems to me that it now is selecting idle state 0 whereas before it was selecting idle state 1 is the correct decision for those very short duration idle states (well, for my processor (older i7-2600K) at least).
Note: I did test my above assertion with kernels compiled with only the first 2 and then 3 of the 8 patch set.
> >> Supporting: trace summary (note: such a heavy load on the trace >> system (~6 gigabytes in 2 minutes) costs about 25% in performance): >> >> k4.16-rc6 pipe >> Idle State 0: Total Entries: 76638 : time (seconds): 0.193166 >> Idle State 1: Total Entries: 37825999 : time (seconds): 23.886772 >> Idle State 2: Total Entries: 49 : time (seconds): 0.007908 >> >> &8patches >> Idle State 0: Total Entries: 37632104 : time (seconds): 26.097220 >> Idle State 1: Total Entries: 397 : time (seconds): 0.020021 >> Idle State 2: Total Entries: 208 : time (seconds): 0.031052 >> >> With rjw 8 patch set (1st col is usecs duration, 2nd col >> is number of occurrences in 2 minutes): >> >> Idle State: 0 Summary: >> 0 24401500 >> 1 13153259 >> 2 19807 >> 3 32731 >> 4 802 >> 5 346 >> 6 1554 >> 7 20087 >> 8 1849 >> 9 150 >> 10 9 >> 11 10 >> >> Idle State: 1 Summary: >> 0 29 >> 1 44 >> 2 15 >> 3 45 >> 4 5 >> 5 26 >> 6 2 >> 7 24
...[snip]... >> >> Kernel 4.19-rc6 reference: >> >> Idle State: 0 Summary: >> 0 17212 >> 1 7516 >> 2 34737 >> 3 14763 >> 4 2312 >> 5 74 >> 6 3 >> 7 3 >> 8 3 >> 9 4 >> 10 5 >> 11 5 >> 40 1 >> >> Idle State: 1 Summary: >> 0 36073601 >> 1 1662728 >> 2 67985 >> 3 106 >> 4 22 >> 5 8 >> 6 2214 >> 7 11037 >> 8 7110
...[snip]...
... Doug
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