linux-kernel - RE: [REGRESSION] Re: [PATCH 00/24] Complete EEVDF

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Message-ID: <000d01db65d4$642acbc0$2c806340$@telus.net>
Date: Mon, 13 Jan 2025 08:01:20 -0800
From: "Doug Smythies" <dsmythies@...us.net>
To: "'Peter Zijlstra'" <peterz@...radead.org>
Cc: <linux-kernel@...r.kernel.org>,
	<vincent.guittot@...aro.org>,
	"'Ingo Molnar'" <mingo@...nel.org>,
	<wuyun.abel@...edance.com>,
	"Doug Smythies" <dsmythies@...us.net>
Subject: RE: [REGRESSION] Re: [PATCH 00/24] Complete EEVDF

On 2025.01.13 03:06 Peter Zijlstra wrote:
> On Sun, Jan 12, 2025 at 03:14:17PM -0800, Doug Smythies wrote:
>
>> The test I have been running to create some of the graphs I have been
>> attaching is a little different, using turbostat with different options:
>> 
>> turbostat --quiet --Summary --show Busy%,Bzy_MHz,IRQ,PkgWatt,PkgTmp,TSC_MHz,Time_Of_Day_Seconds --interval 1
>> 
>> And with this test I get intervals over 1 second by over 10 milliseconds.
>
>> First the b12 kernel (the last good one in the kernel bisection):
>> 
>> Time          Occurrences
>> 1.000000, 3282
>> 1.001000, 1826
>> 1.002000, 227
>> 1.003000, 1852
>> 1.004000, 1036
>> 1.005000, 731
>> 1.006000, 75
>> 1.007000, 30
>> 1.008000, 9
>> 1.009000, 2
>> 1.010000, 1
>> 1.011000, 1
>
> You're creating these Time values from the consecutive
> Time_Of_Day_Seconds data using a script? Let me go check the turbostat
> code to see if my hackery is still invoked, even if not displayed.

Yes, sort of.
I put the output into a spreadsheet and add a column calculating
the time difference between samples.

The histogram is created by a simple c program run against that extracted column.

Anyway, I finally did get some useful information. Examples:

Samp	uSec	Time of day		Delta T		Freq	TSC	IRQ	TMP	PWR
4086	4548	1736734595.017487	1.007149935	4800	4104	12128	73	107.52		
6222	4059	1736736736.520998	1.009660006	4800	4098	12124	74	106.73		
6263	400	1736736777.699340	1.023000002	4800	4104	12345	73	106.51		

The summary histogram line for that capture is:

Total: 9079 : Total >= 10 mSec: 128 ( 1.41 percent)

The maximum uSec was 4548 and there are only about 20 (counted manually) greater
than 1 millisecond (i.e. all good)

The command used was:

turbostat --quiet --Summary --show Busy%,Bzy_MHz,IRQ,PkgWatt,PkgTmp,TSC_MHz,Time_Of_Day_Seconds,usec --interval 1

Anyway, there never is any long time within the turbostat per interval execution.
Any extra time seems to be outside of the main loop.