From: Dave Hansen <dave.hansen@intel.com>
To: "Li, Aubrey" <aubrey.li@linux.intel.com>,
Aubrey Li <aubrey.li@intel.com>,
tglx@linutronix.de, mingo@redhat.com, peterz@infradead.org,
hpa@zytor.com
Cc: ak@linux.intel.com, tim.c.chen@linux.intel.com,
arjan@linux.intel.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 1/2] x86/fpu: track AVX-512 usage of tasks
Date: Thu, 15 Nov 2018 17:04:35 -0800 [thread overview]
Message-ID: <5b7c01b5-dc29-e899-8e32-3ff45061a482@intel.com> (raw)
In-Reply-To: <88a5d6df-0005-db3e-f3be-83e2a8b63a27@linux.intel.com>
On 11/15/18 4:21 PM, Li, Aubrey wrote:
> On 2018/11/15 23:40, Dave Hansen wrote:
>> On 11/14/18 3:00 PM, Aubrey Li wrote:
>>> AVX-512 component has 3 states, only Hi16_ZMM state causes notable
>>> frequency drop. Add per task Hi16_ZMM state tracking to context switch.
>>
>> Just curious, but is there any public documentation of this? It seems
>> really odd to me that something using the same AVX-512 instructions on
>> some low-numbered registers would behave differently than the same
>> instructions on some high-numbered registers. I'm not saying this is
>> wrong, but it's certainly counter-intuitive and I think that begs for
>> some more explanation.
>
> Yes, Intel 64 and IA-32 Architectures software developer's Manual mentioned
> this in performance event CORE_POWER.LVL2_TURBO_LICENSE.
>
> "Core cycles where the core was running with power delivery for license
> level 2 (introduced in Skylake Server microarchitecture). This includes
> high current AVX 512-bit instructions."
>
> I translated license level 2 to frequency drop.
OK, but that talks about AVX 512 and not specifically about Hi16_ZMM's
impact which is what this patch measures. Are the Hi16_ZMM intricacies
documented anywhere?
next prev parent reply other threads:[~2018-11-16 1:04 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-14 23:00 [PATCH v3 1/2] x86/fpu: track AVX-512 usage of tasks Aubrey Li
2018-11-14 23:00 ` [PATCH v3 2/2] proc: add /proc/<pid>/arch_state Aubrey Li
2018-11-15 15:18 ` Dave Hansen
2018-11-16 0:32 ` Li, Aubrey
2018-11-19 17:39 ` Peter Zijlstra
2018-11-21 1:39 ` Li, Aubrey
2018-11-21 8:19 ` Peter Zijlstra
2018-11-21 9:53 ` Peter Zijlstra
2018-11-21 17:12 ` Palmer Dabbelt
2018-11-22 1:40 ` Li, Aubrey
2018-11-23 17:11 ` Dave Martin
2018-11-15 15:40 ` [PATCH v3 1/2] x86/fpu: track AVX-512 usage of tasks Dave Hansen
2018-11-16 0:21 ` Li, Aubrey
2018-11-16 1:04 ` Dave Hansen [this message]
2018-11-16 23:10 ` Dave Hansen
2018-11-17 0:36 ` Li, Aubrey
2018-11-18 14:03 Samuel Neves
2018-11-20 13:20 ` Li, Aubrey
2018-11-20 14:47 ` Samuel Neves
2018-11-26 3:36 ` Li, Aubrey
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