linux-kernel - Re: [PATCH v7] sched: Consolidate cpufreq updates

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Message-ID: <fa2f15b1-1602-4fd0-80ff-9d33303b7b5a@arm.com>
Date: Tue, 8 Oct 2024 10:56:02 +0100
From: Christian Loehle <christian.loehle@....com>
To: Anjali K <anjalik@...ux.ibm.com>, Qais Yousef <qyousef@...alina.io>,
 "Rafael J. Wysocki" <rafael@...nel.org>,
 Viresh Kumar <viresh.kumar@...aro.org>, Ingo Molnar <mingo@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Juri Lelli <juri.lelli@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>, Ben Segall
 <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
 Valentin Schneider <vschneid@...hat.com>, Hongyan Xia
 <hongyan.xia2@....com>, John Stultz <jstultz@...gle.com>,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7] sched: Consolidate cpufreq updates

On 10/7/24 18:20, Anjali K wrote:
> Hi, I tested this patch to see if it causes any regressions on bare-metal power9 systems with microbenchmarks.
> The test system is a 2 NUMA node 128 cpu powernv power9 system. The conservative governor is enabled.
> I took the baseline as the 6.10.0-rc1 tip sched/core kernel.
> No regressions were found.
> 
> +------------------------------------------------------+--------------------+----------+
> |                     Benchmark                        |      Baseline      | Baseline |
> |                                                      |  (6.10.0-rc1 tip   | + patch  |
> |                                                      |  sched/core)       |          |
> +------------------------------------------------------+--------------------+----------+
> |Hackbench run duration (sec)                          |         1          |   1.01   |
> |Lmbench simple fstat (usec)                           |         1          |   0.99   |
> |Lmbench simple open/close (usec)                      |         1          |   1.02   |
> |Lmbench simple read (usec)                            |         1          |   1      |
> |Lmbench simple stat (usec)                            |         1          |   1.01   |
> |Lmbench simple syscall (usec)                         |         1          |   1.01   |
> |Lmbench simple write (usec)                           |         1          |   1      |
> |stressng (bogo ops)                                   |         1          |   0.94   |
> |Unixbench execl throughput (lps)                      |         1          |   0.97   |
> |Unixbench Pipebased Context Switching throughput (lps)|         1          |   0.94   |
> |Unixbench Process Creation (lps)                      |         1          |   1      |
> |Unixbench Shell Scripts (1 concurrent) (lpm)          |         1          |   1      |
> |Unixbench Shell Scripts (8 concurrent) (lpm)          |         1          |   1.01   |
> +------------------------------------------------------+--------------------+----------+
> 
> Thank you,
> Anjali K
> 

The default CPUFREQ_DBS_MIN_SAMPLING_INTERVAL is still to have 2 ticks between
cpufreq updates on conservative/ondemand.
What is your sampling_rate setting? What's your HZ?
Interestingly the context switch heavy benchmarks still show -6% don't they?
Do you mind trying schedutil with a reasonable rate_limit_us, too?

Regards,
Christian