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Date: Sun, 17 May 2020 11:11:43 -0700
From: "Doug Smythies" <dsmythies@...us.net>
To: "'Pratik Rajesh Sampat'" <psampat@...ux.ibm.com>
Cc: <linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>,
<rafael.j.wysocki@...el.com>, <peterz@...radead.org>,
<daniel.lezcano@...aro.org>, <ego@...ux.vnet.ibm.com>,
<svaidy@...ux.ibm.com>, <pratik.sampat@...ibm.com>,
<pratik.r.sampat@...il.com>
Subject: RE: [RFC 0/1] Alternate history mechanism for the TEO governor
On 2020.05.11 Pratik Rajesh Sampat wrote:
>
> First RFC posting: https://lkml.org/lkml/2020/2/22/27
Summary:
On that thread I wrote:
> I have done a couple of other tests with this patch set,
> but nothing to report yet, as the differences have been
> minor so far.
I tried your tests, or as close as I could find, and still
do not notice much difference.
For detail, but likely little added value, read on:
Kernel: 5.7-rc4:
"teo": unmodified kernel.
"wtteo": with this patch added.
"menu": the menu idle governor, for comparison.
CPU frequency scaling driver: intel-cpufreq
CPU frequency scaling governor: schedutil
CPU idle driver: intel_idle
...
> Benchmarks:
> Schbench
> --------
> Benchmarks scheduler wakeup latencies
>
> 1. latency 99th percentile - usec
I found a Phoronix schbench test.
It defaults to 99.9th percentile.
schbench (usec, 99.9th Latency Percentile, less is better)(8 workers)
threads teo wtteo menu
2 14197 14194 99.98% 14467 101.90%
4 46733 46490 99.48% 46554 99.62%
6 57306 58291 101.72% 57754 100.78%
8 81408 80768 99.21% 81715 100.38%
16 157286 156570 99.54% 156621 99.58%
32 314573 310784 98.80% 315802 100.39%
Powers and other idle statistics were similar. [1]
> 2. Power - watts
> Machine - IBM Power 9
>
> Latency and Power - Normalized
> +---------+--------------+-----------------+---------------+
> | Threads | TEO Baseline | Wt. TEO Latency | Wt. TEO Power |
> +---------+--------------+-----------------+---------------+
> | 2 | 100 | 101.3 | 85.29 |
> +---------+--------------+-----------------+---------------+
> | 4 | 100 | 105.06 | 113.63 |
> +---------+--------------+-----------------+---------------+
> | 8 | 100 | 92.32 | 90.36 |
> +---------+--------------+-----------------+---------------+
> | 16 | 100 | 99.1 | 92.43 |
> +---------+--------------+-----------------+---------------+
>
> Accuracy
>
> Vanilla TEO Governor - Prediction distribution %
> +---------+------+------+------+-------+-------+-------+---------+
> | Threads | US 1 | US 2 | US 3 | US 4 | US 5 | US 6 | Correct |
> +---------+------+------+------+-------+-------+-------+---------+
> | 2 | 6.12 | 1.08 | 1.76 | 20.41 | 9.2 | 28.74 | 22.51 |
> +---------+------+------+------+-------+-------+-------+---------+
> | 4 | 8.54 | 1.56 | 1.25 | 20.24 | 10.75 | 25.17 | 22.67 |
> +---------+------+------+------+-------+-------+-------+---------+
> | 8 | 5.88 | 2.67 | 1.09 | 13.72 | 17.08 | 32.04 | 22.95 |
> +---------+------+------+------+-------+-------+-------+---------+
> | 16 | 6.29 | 2.43 | 0.86 | 13.21 | 15.33 | 26.52 | 29.34 |
> +---------+------+------+------+-------+-------+-------+---------+
> +---------+------+------+------+
> | Threads | OS 1 | OS 2 | OS 3 |
> +---------+------+------+------+
> | 2 | 1.77 | 1.27 | 7.14 |
> +---------+------+------+------+
> | 4 | 1.8 | 1.31 | 6.71 |
> +---------+------+------+------+
> | 8 | 0.65 | 0.72 | 3.2 |
> +---------+------+------+------+
> | 16 | 0.63 | 1.71 | 3.68 |
> +---------+------+------+------+
>
> Weighted TEO Governor - Prediction distribution %
> +---------+------+------+------+-------+-------+-------+---------+
> | Threads | US 1 | US 2 | US 3 | US 4 | US 5 | US 6 | Correct |
> +---------+------+------+------+-------+-------+-------+---------+
> | 2 | 7.26 | 2.07 | 0.02 | 15.85 | 13.29 | 36.26 | 22.13 |
> +---------+------+------+------+-------+-------+-------+---------+
> | 4 | 4.33 | 1.45 | 0.15 | 14.17 | 14.68 | 40.36 | 21.01 |
> +---------+------+------+------+-------+-------+-------+---------+
> | 8 | 4.73 | 2.46 | 0.12 | 12.48 | 14.68 | 32.38 | 28.9 |
> +---------+------+------+------+-------+-------+-------+---------+
> | 16 | 7.68 | 1.25 | 0.98 | 12.15 | 11.19 | 24.91 | 35.92 |
> +---------+------+------+------+-------+-------+-------+---------+
> +---------+------+------+------+
> | Threads | OS 1 | OS 2 | OS 3 |
> +---------+------+------+------+
> | 2 | 0.39 | 0.42 | 2.31 |
> +---------+------+------+------+
> | 4 | 0.45 | 0.51 | 2.89 |
> +---------+------+------+------+
> | 8 | 0.53 | 0.66 | 3.06 |
> +---------+------+------+------+
> | 16 | 0.97 | 1.9 | 3.05 |
> +---------+------+------+------+
>
> Sleeping Ebizzy
> ---------------
> Program to generate workloads resembling web server workloads.
> The benchmark is customized to allow for a sleep interval -i
I found a Phoronix ebizzy, but without the customization,
which I suspect is important to demonstrate your potential
improvement.
Could you send me yours to try?
ebizzy (records per second, more is better)
teo wtteo menu
132344 132228 99.91% 130926 98.93%
Powers and other idle statistics were similar. [2]
> 1. Number of records
> 2. Power - watts
> Machine - IBM Power 9
>
> Parameters:
> 1. -m -> Always use mmap instead of malloc
> 2. -M -> Never use mmap
> 3. -S <seconds> -> Number of seconds to run
> 4. -i <interval> -> Sleep interval
What are the units of this interval?
They must be microseconds, as that is the only thing that makes sense.
I have tried to simulate the resulting actual workflow
myself, but didn't get results like yours. (I may have done a poorly.)
My test does not produce performance data, as it just has to do its work
before the next time to do a chunk of work.
The test is:
forever
do 100 times
very short sleep
enddo
sleep for 10 milliseconds
endforever
The overheads result in enough activity.
Powers and other idle statistics were similar. [3]
>
> Number of records and power normalized
> +-------------------+---------------+------------------+-----------------+
> | Parameters | TEO baseline | Wt TEO records | Wt. TEO Power |
> +-------------------+---------------+------------------+-----------------+
> | -S 60 -i 10000 | 100 | 106.56 | 93.95 |
> +-------------------+---------------+------------------+-----------------+
> | -m -S 60 -i 10000 | 100 | 100.62 | 82.14 |
> +-------------------+---------------+------------------+-----------------+
> | -M -S 60 -i 10000 | 100 | 104.97 | 95.19 |
> +-------------------+---------------+------------------+-----------------+
>
> Accuracy
>
> Vanilla TEO Governor - Prediction distribution %
> +-------------------+-------+------+------+-------+------+-------+
> | Parameters | US 1 | US 2 | US 3 | US 4 | US 5 | US 6 |
> +-------------------+-------+------+------+-------+------+-------+
> | -S 60 -i 10000 | 45.46 | 0.52 | 1.5 | 15.34 | 2.44 | 8.61 |
> +-------------------+-------+------+------+-------+------+-------+
> | -m -S 60 -i 10000 | 4.22 | 2.08 | 0.71 | 90.01 | 0 | 0.01 |
> +-------------------+-------+------+------+-------+------+-------+
> | -M -S 60 -i 10000 | 15.78 | 1.42 | 2.4 | 22.39 | 1.68 | 11.25 |
> +-------------------+-------+------+------+-------+------+-------+
> +-------------------+---------+------+------+------+------+
> | Parameters | Correct | OS 1 | OS 2 | OS 3 | OS 4 |
> +-------------------+---------+------+------+------+------+
> | -S 60 -i 10000 | 17.03 | 1.73 | 1.1 | 6.27 | 0 |
> +-------------------+---------+------+------+------+------+
> | -m -S 60 -i 10000 | 2.44 | 0.18 | 0.13 | 0.22 | 0 |
> +-------------------+---------+------+------+------+------+
> | -M -S 60 -i 10000 | 31.65 | 3.45 | 1.8 | 8.18 | 0 |
> +-------------------+---------+------+------+------+------+
>
> Weigted TEO Governor - Prediction distribution %
> +-------------------+-------+------+------+-------+------+-------+
> | Parameters | US 1 | US 2 | US 3 | US 4 | US 5 | US 6 |
> +-------------------+-------+------+------+-------+------+-------+
> | -S 60 -i 10000 | 8.25 | 0.87 | 0.98 | 19.23 | 4.05 | 26.35 |
> +-------------------+-------+------+------+-------+------+-------+
> | -m -S 60 -i 10000 | 7.69 | 4.35 | 0.93 | 82.74 | 0.01 | 0.01 |
> +-------------------+-------+------+------+-------+------+-------+
> | -M -S 60 -i 10000 | 3.73 | 3.29 | 0.73 | 13.33 | 7.38 | 18.61 |
> +-------------------+-------+------+------+-------+------+-------+
> +-------------------+---------+------+------+------+------+
> | Parameters | Correct | OS 1 | OS 2 | OS 3 | OS 4 |
> +-------------------+---------+------+------+------+------+
> | -S 60 -i 10000 | 32.86 | 3.27 | 2.05 | 2.09 | 0 |
> +-------------------+---------+------+------+------+------+
> | -m -S 60 -i 10000 | 3.4 | 0.29 | 0.28 | 0.3 | 0 |
> +-------------------+---------+------+------+------+------+
> | -M -S 60 -i 10000 | 48.19 | 1.8 | 0.93 | 1.97 | 0.04 |
> +-------------------+---------+------+------+------+------+
For accuracy numbers, it would help to know the sample size
and the importance.
For this 60 second test, I wonder if the number of times
each idle state was entered and exited was large enough to
draw any conclusion. I often find for tests that some states are
only used a few times in 1 minute, and so don't really care about the accuracy.
Anyway, for my attempts that this test, I had to extend to a 5 minute sample
time to get adequate numbers in all idle states for the accuracy statistics.
(which showed no difference, by the way (for those not looking at the graphs).)
For my test all three governors, teo, wtteo, and menu, were
using idle state 0 about 7 to 8 thousand times per 5 minutes,
and 100% of time the assessment was the state was too shallow.
However, I don't really care because it is only 0.003% of the time,
and if idle state 0 is disabled (teo-0disable on [3] (it is enabled
again at minute 35), the power doesn't change.
All that being said, your power/accuracy results do seem correlated.
>
> Pgbench
> -------
> pgbench is a simple program for running benchmark tests on PostgreSQL.
> It runs the same sequence of SQL commands over and over, possibly in
> multiple concurrent database sessions, and then calculates the average
> transaction rate (transactions per second).
I did not try this test or anything similar.
...
>
> Hackbench
> ---------
> Creates a specified number of pairs of schedulable entities
> which communicate via either sockets or pipes and time how long it
> takes for each pair to send data back and forth.
>
I found a Phoronix version, but it doesn't like
your low loops counts, so I stayed with the default 50,000.
I suspect your low loop count results in a workflow somewhat like
your special ebizzy test. Anyway, maybe I should try your version
and low loop counts.
I did many tests, and get inconsistent results.
You use these terms like "sockets" and "pipes", but
the phoronix test uses "count" and "thread" or "process".
I only used "process" for the simple reason that there was very
very little use of idle at all with "thread", so there was no value
in any test.
hackbench test 1: all - process (seconds, less is better)
test count teo wtteo menu
1 1 8.7 8.99 103.33% 9.071 104.26%
2 2 16.509 16.96 102.73% 17.159 103.94%
3 4 33.451 34.081 101.88% 34.101 101.94%
4 8 69.037 71.647 103.78% 69.914 101.27%
5 16 161.64 165.569 102.43% 165.015 102.09%
Powers and other idle statistics were similar. [4]
hackbench test 2: count 1 - process (seconds, less is better)
teo wtteo menu
average 8.906 8.703 97.72% 9.032 101.41%
max 9.263 8.856 9.228
min 8.761 8.599 8.876
Std. Dev. 0.83% 0.46% 0.80%
runs 256 256 200
Powers and other idle statistics were similar. [5]
However, idle state 3 is worthy of a look.
hackbench test 3: count 2 - process (seconds, less is better)
teo wtteo menu
average 16.702 16.65 99.69% 16.796 100.56%
max 16.853 16.966 17.058
min 16.542 16.487 16.659
Std. Dev. 0.41% 0.59% 0.56%
runs 100 100 100
Powers and other idle statistics were similar. [6]
However, idle state 3 is worthy of a look.
> Machine - IBM Power 9
>
> Scale of measurement:
> 1. Time (s)
> 2. Power (watts)
> Time is normalized
>
> +---------+----------+----------------------+-------------------+
> | Loops | TEO Time | Wt. TEO Time Sockets | Wt. TEO Time Pipe |
> +---------+----------+----------------------+-------------------+
> | 100 | 100 | 95.23 | 87.09 |
> +---------+----------+----------------------+-------------------+
> | 1000 | 100 | 105.81 | 98.67 |
> +---------+----------+----------------------+-------------------+
> | 10000 | 100 | 99.33 | 92.73 |
> +---------+----------+----------------------+-------------------+
> | 100000 | 100 | 98.88 | 101.99 |
> +---------+----------+----------------------+-------------------+
> | 1000000 | 100 | 100.04 | 100.2 |
> +---------+----------+----------------------+-------------------+
>
> Power :Socket: Consistent between 135-140 watts for both TEO and Wt. TEO
> Pipe: Consistent between 125-130 watts for both TEO and Wt. TEO
>
> Pratik Rajesh Sampat (1):
> Weighted approach to gather and use history in TEO governor
>
> drivers/cpuidle/governors/teo.c | 96 +++++++++++++++++++++++++++++++--
> 1 file changed, 91 insertions(+), 5 deletions(-)
>
> --
> 2.17.1
I also tried Giovanni's and Mel's mmtests, (uses idle states 0 and 1 a lot)
but couldn't extract the performance report. [7]
Old sweep test, which doesn't produce performance data. [8]
Old system idle test. [9]
[1] http://www.smythies.com/~doug/linux/idle/wtteo/schbench/
[2] http://www.smythies.com/~doug/linux/idle/wtteo/ebizzy/
[3] http://www.smythies.com/~doug/linux/idle/wtteo/pn01/
[4] http://www.smythies.com/~doug/linux/idle/wtteo/hackbench/
[5] http://www.smythies.com/~doug/linux/idle/wtteo/hackbench2/
[6] http://www.smythies.com/~doug/linux/idle/wtteo/hackbench3/
[7] http://www.smythies.com/~doug/linux/idle/wtteo/mmtests-udp/
[8] http://www.smythies.com/~doug/linux/idle/wtteo/sweep/
[9] http://www.smythies.com/~doug/linux/idle/wtteo/idle/
... Doug
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