linux-kernel - Re: [PATCH v3 2/2] proc: add /proc/<pid>/arch

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Date:   Thu, 22 Nov 2018 09:40:24 +0800
From:   "Li, Aubrey" <aubrey.li@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>
Cc:     Aubrey Li <aubrey.li@...el.com>, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, ak@...ux.intel.com,
        tim.c.chen@...ux.intel.com, dave.hansen@...el.com,
        arjan@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] proc: add /proc/<pid>/arch_state

On 2018/11/21 17:53, Peter Zijlstra wrote:
> On Wed, Nov 21, 2018 at 09:19:36AM +0100, Peter Zijlstra wrote:
>> On Wed, Nov 21, 2018 at 09:39:00AM +0800, Li, Aubrey wrote:
>>>> Also; you were going to shop around with the other architectures to see
>>>> what they want/need for this interface. I see nothing on that.
>>>>
>>> I'm open for your suggestion, :)
>>
>> Well, we have linux-arch and the various maintainers are also listed in
>> MAINTAINERS. Go forth and ask..
> 
> Ok, so I googled a wee bit (you could have too).
> 
> There's not that many architectures that build big hot chips
> (powerpc,x86,arm64,s390) (mips, sparc64 and ia64 are pretty dead I
> think, although the Fujitsu Sparc M10 X+/X SIMD looked like it could be
> 'fun').
> 
> Of those, powerpc altivec doesn't seem to be very wide, but you'd have
> to ask the power folks. Same for s390 z13.
> 
> The Fujitsu/ARM64-SVE stuff looks like it can be big and hot.
> 
> And RISC-V has was vector extention, but I don't think anybody is
> actually building big hot versions of that just yet.
> 
Thanks Peter. Add more maintainers here.

On some x86 architectures, the tasks using simd instruction(AVX512 particularly)
need to be dealt with specially against the tasks not using simd instruction.
I proposed an interface to expose such CPU specific information for the user
space tools to apply different scheduling policies.

The interface can be refined to be the format as /proc/<pid>/status. Not sure
if it's useful to any other architectures.

Welcome any comments.

Thanks,
-Aubrey