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From: Andreas Herrmann <aherrmann@suse.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
	linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Stratos Karafotis <stratosk@semaphore.gr>,
	Thomas Renninger <trenn@suse.com>
Subject: Re: [PATCH 1/1] cpufreq: pcc-cpufreq: Re-introduce deadband effect to reduce number of frequency changes
Date: Wed, 14 Sep 2016 16:56:43 +0200	[thread overview]
Message-ID: <20160914145643.GA19982@suselix.suse.de> (raw)
In-Reply-To: <20160907050201.GK27345@vireshk-i7>

On Wed, Sep 07, 2016 at 10:32:01AM +0530, Viresh Kumar wrote:
> On 01-09-16, 15:21, Andreas Herrmann wrote:

  ---8<---

> > I started with the value return as "nominal latency" for PCC.  This
> > was 300000 ns on the test system and made things worse.  I've tested
> > other values as well unitl I've found a local optimium at 45000ns but
> > performance was lower in comparison to when I've applied my hack.
> 
> Can you try to use kernel tracer (ftrace) and see how the frequencies
> are getting changed and at what frequency.

Below is some trace data. I hope it is of some help.

(A) - sampling 10s period when system is idle
(B) - sampling 10s period when system partially loaded (kernel
      compilation using 2 jobs)

(1) 4.8-rc5
(2) 4.8-rc5 with my patch (reintro of deadband effect within
    pcc-cpufreq)
(3) 4.8-rc5 with reversal of 6393d6a102 (cpufreq: ondemand: Eliminate
    the deadband effect)

Let me know whether you are looking for other trace data wrt this
issue.


Thanks,

Andreas

---

(A)-(1)

 # Total Lost Samples: 0
 # Samples: 41  of event 'power:cpu_frequency'
 # Event count (approx.): 41
 # Overhead  Command       Shared Object     Symbol                       
 # ........  ............  ................  .............................
     39.02%  kworker/14:1  [kernel.vmlinux]  [k] cpufreq_notify_transition
     29.27%  kworker/0:0   [kernel.vmlinux]  [k] cpufreq_notify_transition
     19.51%  kworker/10:1  [kernel.vmlinux]  [k] cpufreq_notify_transition
      7.32%  kworker/5:2   [kernel.vmlinux]  [k] cpufreq_notify_transition
      2.44%  kworker/23:2  [kernel.vmlinux]  [k] cpufreq_notify_transition
      2.44%  kworker/40:1  [kernel.vmlinux]  [k] cpufreq_notify_transition

(A)-(2)

 # Total Lost Samples: 0
 # Samples: 6  of event 'power:cpu_frequency'
 # Event count (approx.): 6
 # Overhead  Command       Shared Object     Symbol                       
 # ........  ............  ................  .............................
     33.33%  kworker/1:2   [kernel.vmlinux]  [k] cpufreq_notify_transition
     16.67%  kworker/16:1  [kernel.vmlinux]  [k] cpufreq_notify_transition
     16.67%  kworker/22:1  [kernel.vmlinux]  [k] cpufreq_notify_transition
     16.67%  kworker/26:1  [kernel.vmlinux]  [k] cpufreq_notify_transition
     16.67%  kworker/33:1  [kernel.vmlinux]  [k] cpufreq_notify_transition

(A)-(3)

 # Total Lost Samples: 0
 # Samples: 7  of event 'power:cpu_frequency'
 # Event count (approx.): 7
 # Overhead  Command       Shared Object     Symbol                       
 # ........  ............  ................  .............................
     28.57%  kworker/58:1  [kernel.vmlinux]  [k] cpufreq_notify_transition
     14.29%  kworker/19:2  [kernel.vmlinux]  [k] cpufreq_notify_transition
     14.29%  kworker/20:2  [kernel.vmlinux]  [k] cpufreq_notify_transition
     14.29%  kworker/22:2  [kernel.vmlinux]  [k] cpufreq_notify_transition
     14.29%  kworker/23:1  [kernel.vmlinux]  [k] cpufreq_notify_transition
     14.29%  kworker/35:1  [kernel.vmlinux]  [k] cpufreq_notify_transition

---

(B)-(1)

 # Total Lost Samples: 0
 # Samples: 2K of event 'power:cpu_frequency'
 # Event count (approx.): 2382
 # Overhead  Command       Shared Object     Symbol                       
 # ........  ............  ................  .............................
      5.75%  kworker/0:0   [kernel.vmlinux]  [k] cpufreq_notify_transition
      4.16%  kworker/12:2  [kernel.vmlinux]  [k] cpufreq_notify_transition
      3.11%  kworker/17:1  [kernel.vmlinux]  [k] cpufreq_notify_transition
      2.94%  kworker/2:1   [kernel.vmlinux]  [k] cpufreq_notify_transition
      2.73%  kworker/19:1  [kernel.vmlinux]  [k] cpufreq_notify_transition
      ...

(B)-(2)

 # Total Lost Samples: 0
 # Samples: 320  of event 'power:cpu_frequency'
 # Event count (approx.): 320
 # Overhead  Command       Shared Object     Symbol                       
 # ........  ............  ................  .............................
      4.69%  kworker/56:1  [kernel.vmlinux]  [k] cpufreq_notify_transition
      4.06%  kworker/12:1  [kernel.vmlinux]  [k] cpufreq_notify_transition
      4.06%  kworker/28:1  [kernel.vmlinux]  [k] cpufreq_notify_transition
      4.06%  kworker/6:2   [kernel.vmlinux]  [k] cpufreq_notify_transition
      3.75%  kworker/32:2  [kernel.vmlinux]  [k] cpufreq_notify_transition
      ...

(B)-(3)

 # Total Lost Samples: 0
 # Samples: 333  of event 'power:cpu_frequency'
 # Event count (approx.): 333
 # Overhead  Command       Shared Object     Symbol                       
 # ........  ............  ................  .............................
      4.80%  kworker/51:1  [kernel.vmlinux]  [k] cpufreq_notify_transition
      4.50%  kworker/39:1  [kernel.vmlinux]  [k] cpufreq_notify_transition
      4.20%  kworker/47:1  [kernel.vmlinux]  [k] cpufreq_notify_transition
      3.90%  kworker/59:1  [kernel.vmlinux]  [k] cpufreq_notify_transition
      3.90%  kworker/7:2   [kernel.vmlinux]  [k] cpufreq_notify_transition
      ...

---

With (1) pcc-cpufreq tries to set pretty much every frequency even if
the system is idle, e.g. here is the start of (perf script output)
from (A)-(1):

     kworker/5:2   904 [005]   255.778343: power:cpu_frequency: state=1216000 cpu_id=5
     kworker/5:2   904 [005]   255.794382: power:cpu_frequency: state=1264000 cpu_id=5
     kworker/5:2   904 [005]   256.102400: power:cpu_frequency: state=1200000 cpu_id=5
    kworker/10:1   171 [010]   258.010362: power:cpu_frequency: state=2224000 cpu_id=10
    kworker/10:1   171 [010]   258.026366: power:cpu_frequency: state=1264000 cpu_id=10
    kworker/10:1   171 [010]   258.594514: power:cpu_frequency: state=1200000 cpu_id=10
    kworker/10:1   171 [010]   258.618417: power:cpu_frequency: state=1232000 cpu_id=10
    kworker/10:1   171 [010]   258.634409: power:cpu_frequency: state=1264000 cpu_id=10
    kworker/10:1   171 [010]   258.674467: power:cpu_frequency: state=1200000 cpu_id=10
    kworker/10:1   171 [010]   258.730486: power:cpu_frequency: state=1216000 cpu_id=10
    kworker/40:1   388 [040]   258.730999: power:cpu_frequency: state=1200000 cpu_id=40
    kworker/23:2   775 [023]   258.731504: power:cpu_frequency: state=1200000 cpu_id=23
    kworker/14:1   178 [014]   258.732013: power:cpu_frequency: state=1216000 cpu_id=14
    kworker/10:1   171 [010]   258.906434: power:cpu_frequency: state=1200000 cpu_id=10
    kworker/14:1   178 [014]   258.970500: power:cpu_frequency: state=1200000 cpu_id=14
    kworker/14:1   178 [014]   258.998440: power:cpu_frequency: state=1232000 cpu_id=14
    kworker/14:1   178 [014]   259.034490: power:cpu_frequency: state=1200000 cpu_id=14
    kworker/14:1   178 [014]   259.095089: power:cpu_frequency: state=1216000 cpu_id=14
    kworker/14:1   178 [014]   259.270470: power:cpu_frequency: state=1200000 cpu_id=14
    ...

  parent reply	other threads:[~2016-09-14 14:57 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-19 12:18 [PATCH 0/1] cpufreq: pcc-cpufreq: Re-introduce deadband effect to reduce number of frequency changes Andreas Herrmann
2016-08-19 12:21 ` [PATCH 1/1] " Andreas Herrmann
2016-08-29  6:01   ` Viresh Kumar
2016-09-01 13:21     ` Andreas Herrmann
2016-09-07  5:02       ` Viresh Kumar
2016-09-13 10:53         ` Andreas Herrmann
2016-09-14 14:56         ` Andreas Herrmann [this message]
2016-10-05  5:17           ` Viresh Kumar
2016-10-11  6:28             ` Andreas Herrmann
2016-09-16  9:47         ` Andreas Herrmann
2016-09-16 18:48           ` Stratos Karafotis
     [not found]             ` <CADmjqpNE9f7fzQjWsHKB4wEjLq-4ZvQpaC314OcLdQ-i_TAABg@mail.gmail.com>
2016-09-19 16:16               ` Andreas Herrmann
2016-09-19 19:39                 ` Stratos Karafotis
2016-09-22 17:54                   ` Andreas Herrmann
2016-10-05  5:21                     ` Viresh Kumar
2016-08-19 12:40 ` [PATCH 0/1] " Andreas Herrmann
2016-09-23 16:56 ` [PATCH v2 0/2] " Andreas Herrmann
2016-09-23 17:02   ` [PATCH v2 1/2] cpufreq/ondemand: Introduce op to customize mapping of load to frequency Andreas Herrmann
2016-10-05  4:01     ` Viresh Kumar
2016-10-11  6:30       ` Andreas Herrmann
2016-09-23 17:07   ` [PATCH v2 2/2] cpufreq/pcc-cpufreq: Make use of map_load_to_freq op Andreas Herrmann
2016-09-26  9:05     ` [PATCH v3 " Andreas Herrmann

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