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

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Message-ID: <20250121112140.GJ8385@noisy.programming.kicks-ass.net>
Date: Tue, 21 Jan 2025 12:21:40 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Doug Smythies <dsmythies@...us.net>
Cc: linux-kernel@...r.kernel.org, vincent.guittot@...aro.org,
	'Ingo Molnar' <mingo@...nel.org>, wuyun.abel@...edance.com
Subject: Re: [REGRESSION] Re: [PATCH 00/24] Complete EEVDF

On Tue, Jan 21, 2025 at 09:49:08AM +0100, Peter Zijlstra wrote:

> > I modified your tracing trigger thing in turbostat to this:
> 
> Shiny!
> 
> What turbostat invocation do I use? I think the last I had was:
> 
>   tools/power/x86/turbostat/turbostat --quiet --show Busy%,IRQ,Time_Of_Day_Seconds,CPU,usec --interval 1
> 
> I've started a new run of yes-vs-turbostate with the modified trigger
> condition. Lets see what pops out.

Ok, I have a trace.o

So I see turbostat wake up on CPU 15, do its migration round 0-15 and
when its back at 15 it prints the WHOOPSIE.

(trimmed trace):

             yes-1169    [015] dNh4.  4238.261759: sched_wakeup: comm=turbostat pid=1185 prio=100 target_cpu=015
             yes-1169    [015] d..2.  4238.261761: sched_switch: prev_comm=yes prev_pid=1169 prev_prio=120 prev_state=R ==> next_comm=turbostat next_pid=1185 next_prio=100
    migration/15-158     [015] d..3.  4238.261977: sched_migrate_task: comm=turbostat pid=1185 prio=100 orig_cpu=15 dest_cpu=0
     migration/0-20      [000] d..3.  4238.261991: sched_migrate_task: comm=turbostat pid=1185 prio=100 orig_cpu=0 dest_cpu=1
     migration/1-116     [001] d..3.  4238.262003: sched_migrate_task: comm=turbostat pid=1185 prio=100 orig_cpu=1 dest_cpu=2
     migration/2-25      [002] d..3.  4238.262018: sched_migrate_task: comm=turbostat pid=1185 prio=100 orig_cpu=2 dest_cpu=3
     migration/3-122     [003] d..3.  4238.262031: sched_migrate_task: comm=turbostat pid=1185 prio=100 orig_cpu=3 dest_cpu=4
     migration/4-31      [004] d..3.  4238.262044: sched_migrate_task: comm=turbostat pid=1185 prio=100 orig_cpu=4 dest_cpu=5
     migration/5-128     [005] d..3.  4238.262057: sched_migrate_task: comm=turbostat pid=1185 prio=100 orig_cpu=5 dest_cpu=6
     migration/6-37      [006] d..3.  4238.262071: sched_migrate_task: comm=turbostat pid=1185 prio=100 orig_cpu=6 dest_cpu=7
     migration/7-134     [007] d..3.  4238.262084: sched_migrate_task: comm=turbostat pid=1185 prio=100 orig_cpu=7 dest_cpu=8
     migration/8-43      [008] d..3.  4238.262097: sched_migrate_task: comm=turbostat pid=1185 prio=100 orig_cpu=8 dest_cpu=9
     migration/9-140     [009] d..3.  4238.262109: sched_migrate_task: comm=turbostat pid=1185 prio=100 orig_cpu=9 dest_cpu=10
    migration/10-49      [010] d..3.  4238.262123: sched_migrate_task: comm=turbostat pid=1185 prio=100 orig_cpu=10 dest_cpu=11
    migration/11-146     [011] d..3.  4238.262136: sched_migrate_task: comm=turbostat pid=1185 prio=100 orig_cpu=11 dest_cpu=12
    migration/12-55      [012] d..3.  4238.262150: sched_migrate_task: comm=turbostat pid=1185 prio=100 orig_cpu=12 dest_cpu=13
    migration/13-152     [013] d..3.  4238.262164: sched_migrate_task: comm=turbostat pid=1185 prio=100 orig_cpu=13 dest_cpu=14
    migration/14-62      [014] d..3.  4238.262177: sched_migrate_task: comm=turbostat pid=1185 prio=100 orig_cpu=14 dest_cpu=15
             yes-1169    [015] d..2.  4238.262182: sched_switch: prev_comm=yes prev_pid=1169 prev_prio=120 prev_state=R+ ==> next_comm=turbostat next_pid=1185 next_prio=100
       turbostat-1185    [015] .....  4238.262189: __x64_sys_gettimeofday: WHOOPSIE!

The time between wakeup and whoopsie 4238.262189-4238.261759 = .000430
or 430us, which doesn't seem excessive to me.

Let me go read this turbostat code to figure out what exactly the
trigger condition signifies. Because I'm not seeing nothing weird here.