linux-kernel - Re: [PATCH 0/9] Add CPU-type to topology

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Message-ID: <20240627125340.GB4743@ranerica-svr.sc.intel.com>
Date: Thu, 27 Jun 2024 05:53:40 -0700
From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To: srinivas pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
	Brice Goglin <brice.goglin@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	daniel.sneddon@...ux.intel.com, tony.luck@...el.com,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-perf-users@...r.kernel.org,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	Andrew Cooper <andrew.cooper3@...rix.com>
Subject: Re: [PATCH 0/9] Add CPU-type to topology

On Wed, Jun 19, 2024 at 03:34:46AM -0700, srinivas pandruvada wrote:

[...]

> > 
> > There can be many ways to expose this information in sysfs. Like this
> > ...
> > 
> > > [1] https://lkml.org/lkml/2020/10/2/1208
> > 
> > ... exposes /sys/devices/system/cpu/types which, in hybrid parts,
> > creates a
> > subdirectory for each type of CPU. Each subdirectory contains a CPU
> > list
> > and a CPU map that user space can query.
> > 
> > The other way is to expose the CPU-type in a file:
> > 
> >         /sys/devices/system/cpu/cpuN/type
> > 
> > that could return the CPU-type of the CPU N. Is there a preference?
> 
> But you still have to look at frequency or caches as there are Low
> power E-cores which will have same type but different capabilities.

By the way, /sys/devices/system/cpuN/cache is broken on these systems with
low power Ecores. I proposed a patch to fix it here [B]. May I ask for a few
extra reviews and testing? Perhaps this will raise the confidence of the
x86 maintainers? :)

The patchset continues to apply cleanly on v6.10-rc5.

[B]. https://lore.kernel.org/all/20231212222519.12834-5-ricardo.neri-calderon@linux.intel.com/