linux-kernel - Re: [PATCH v2] ACPI: Replace msleep() with usleep_range() in acpi_os

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Message-ID: <dbc2892f-0735-4510-9509-b225b65537c9@arm.com>
Date: Wed, 20 Nov 2024 13:06:58 +0100
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Pierre Gondois <pierre.gondois@....com>,
 "Rafael J. Wysocki" <rafael@...nel.org>, Hans de Goede <hdegoede@...hat.com>
Cc: Len Brown <lenb@...nel.org>, anna-maria@...utronix.de,
 tglx@...utronix.de, peterz@...radead.org, frederic@...nel.org,
 corbet@....net, akpm@...ux-foundation.org, linux-acpi@...r.kernel.org,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
 Len Brown <len.brown@...el.com>, Arjan van de Ven <arjan@...ux.intel.com>,
 Todd Brandt <todd.e.brandt@...el.com>
Subject: Re: [PATCH v2] ACPI: Replace msleep() with usleep_range() in
 acpi_os_sleep().

On 20/11/2024 10:01, Pierre Gondois wrote:
> 
> 
> On 11/18/24 13:02, Rafael J. Wysocki wrote:
>> Hi Hans,
>>
>> On Mon, Nov 18, 2024 at 12:38 PM Hans de Goede <hdegoede@...hat.com>
>> wrote:
>>>
>>> Hi Rafael, Len,
>>>
>>> On 18-Nov-24 12:03 PM, Rafael J. Wysocki wrote:
>>>> On Sat, Nov 16, 2024 at 12:11 AM Len Brown <lenb@...nel.org> wrote:

[...]

> FWIW, testing the above version on an Arm Juno platform by executing
> the following method:
> 
> Method (SLEE, 1, Serialized)  {
>   Sleep(Arg0)
> }
> 
> _wo: without patch
> _w: with patch
> - Values in ns.
> - Requesting to sleep X ms
> - Tested over 10 iterations
> - HZ=250
> +------+------------+----------+------------+---------+-----------+
> |   ms |    mean_wo |   std_wo |    mean_w  |  std_w  |     ratio |
> +------+------------+----------+------------+---------+-----------+
> |    1 |    8087797 |  2079703 |    1313920 |   55066 | -83.75429 |
> |    2 |    7942471 |  2201985 |    2416064 |  111604 | -69.58044 |
> |    3 |    8373704 |   144274 |    3632537 |  111037 | -56.61970 |
> |    4 |    7946013 |  2214330 |    4606028 |  255838 | -42.03346 |
> |    5 |   11418920 |  1673914 |    5955548 |  131862 | -47.84490 |
> |    6 |   11427042 |  1677519 |    7045713 |  211439 | -38.34176 |
> |    7 |   12301242 |   221580 |    8174633 |  330050 | -33.54628 |
> |    8 |   11411606 |  1672182 |    9191048 |  431767 | -19.45877 |
> |    9 |   16722304 |  1288625 |   10517284 |  103274 | -37.10625 |
> |   10 |   16746542 |  1280385 |   11564426 |  417218 | -30.94439 |
> |   20 |   24294957 |    70703 |   22756497 |  673936 |  -6.33243 |
> |   30 |   36284782 |    74340 |   34131455 |  391473 |  -5.93452 |
> |   40 |   44703162 |  1199709 |   45407108 |  289715 |   1.57471 |
> |   50 |   56311282 |   281418 |   56098040 |  607739 |  -0.37868 |
> |   60 |   64225811 |   247587 |   64302246 |  132059 |   0.11901 |
> |   70 |   76299457 |    99853 |   76282497 |   83910 |  -0.02223 |
> |  100 |  104214393 |    38642 |  104212524 |  244424 |  -0.00179 |
> | 1000 | 1016131215 |   245725 | 1017051744 | 2748280 |   0.09059 |
> | 2000 | 2007711297 |  1325094 | 2007628922 | 1421807 |  -0.00410 |
> +------+------------+----------+------------+---------+-----------+
> - With the patch, the min sleep duration is never below the requested
>   sleep duration
> 
> So indeed the penalty of using msleep is big for small sleep durations.

Just to make sure, this is with Rafael's proposal, using msleep() for
values >= 48ms = (12 * 1000/250)ms and usleep_range() otherwise?