Re: [PATCH v2 0/2] intel_powerclamp: New module parameter

[srinivas pandruvada]

On Tue, 2023-02-07 at 05:42 -0800, Ricardo Neri wrote:
> On Mon, Feb 06, 2023 at 02:02:28AM -0800, srinivas pandruvada wrote:
> > On Mon, 2023-02-06 at 08:05 +0000, Zhang, Rui wrote:
> > > On Sun, 2023-02-05 at 18:45 -0800, srinivas pandruvada wrote:
> > > > Hi Rui,
> > > > 
> > > > On Sun, 2023-02-05 at 15:57 +0000, Zhang, Rui wrote:
> > > > > Hi, Srinivas,
> > > > > 
> > > > > First of all, the previous build error is gone.
> > > > > 
> > > > > Second, I found something strange, which may be related with
> > > > > the
> > > > > scheduler asym-packing, so CC Ricardo.
> > > > > 
> > > > I thought you disable ITMT before idle injection and reenebale
> > > > after
> > > > removal.
> > > 
> > > No.
> > > 
> > > I can reproduce this by playing with raw intel_powerclamp sysfs
> > > knobs
> > > and ITMT enabled.
> > > 
> > 
> > This issue is happening even if ITMT disabled. If the module mask
> > is
> > composed of P-cores it works or even on servers as expected.
> > Also if you offline all P-cores then select mask among E-cores, it
> > is
> > working. Somehow P-core influences E-cores.
> > 
> > Since this patch is module mask related, that is functioning
> > correctly.
> > We have to debug this interaction with P and E cores separately.
> 
> Currently, when doing asym_packing, ECores will only pull tasks from
> a
> PCore only if both SMT siblings are busy. It will only pull from the
> lower-priority sibling. These patches [1] let ECores pull from either
> sibling, if both are busy.
> 
> I presume that by injecting idle, the scheduler thinks that the CPU
> is
> idle (i.e., idle_cpu() returns true) and it will not do asym_packing
> from
> lower-priority CPUs.
> 
> However, in your experiment you have 16 threads. If a Pcore is
> overloaded,
> an ECore should be able to help.
This issue happens with or without ITMT and also without any idle
injection active.

Thanks,
Srinivas


> 
> [1].
> https://lore.kernel.org/lkml/20230207045838.11243-1-ricardo.neri-calderon@xxxxxxxxxxxxxxx/
>