From: Dave Hansen <dave.hansen@intel.com>
To: Andi Kleen <ak@linux.intel.com>,
"Li, Aubrey" <aubrey.li@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Aubrey Li <aubrey.li@intel.com>,
mingo@redhat.com, peterz@infradead.org, hpa@zytor.com,
tim.c.chen@linux.intel.com, arjan@linux.intel.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 1/3] x86/fpu: track AVX-512 usage of tasks
Date: Tue, 18 Dec 2018 13:44:41 -0800 [thread overview]
Message-ID: <d892d7bb-2a66-497c-4728-138c8e5e077f@intel.com> (raw)
In-Reply-To: <20181218213826.GI25620@tassilo.jf.intel.com>
On 12/18/18 1:38 PM, Andi Kleen wrote:
>> I misunderstood, you mean 32bit kernel, not 32bit machine. Theoretically 32bit
>> kernel can use AVX512, but not sure if anyone use it like this. get_jiffies_64()
>> includes jiffies_lock ops so not good in context switch. So I want to use raw
>> jiffies_64 here. jiffies is a good candidate but it has wraparound overflow issue.
>> Other time source are expensive here.
>>
>> Should I limit the code only running on 64bit kernel?
> Yes making it 64bit only should be fine.
I think I'd rather just disable AVX512 itself on 32-bit and be done with
it. I think more than half of the ~2k of XSAVE space that it consumes
in *every* *task* is just pure waste because it has to be 0's.
This ~2k of extra space is also lowmem, which makes it even more valuable.
next prev parent reply other threads:[~2018-12-18 21:44 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-18 4:22 [PATCH v6 1/3] x86/fpu: track AVX-512 usage of tasks Aubrey Li
2018-12-18 4:22 ` [PATCH v6 2/3] proc: add AVX-512 usage elapsed time to /proc/pid/status Aubrey Li
2018-12-18 4:22 ` [PATCH v6 3/3] Documentation/filesystems/proc.txt: add AVX512_elapsed_ms Aubrey Li
2018-12-18 14:14 ` [PATCH v6 1/3] x86/fpu: track AVX-512 usage of tasks Thomas Gleixner
2018-12-18 15:11 ` Li, Aubrey
2018-12-18 15:32 ` Thomas Gleixner
2018-12-18 16:28 ` Li, Aubrey
2018-12-18 21:38 ` Andi Kleen
2018-12-18 21:44 ` Dave Hansen [this message]
2018-12-18 22:05 ` Andi Kleen
2018-12-19 0:26 ` Li, Aubrey
2018-12-19 9:45 ` Thomas Gleixner
2018-12-18 17:14 ` Dave Hansen
2018-12-18 23:23 ` Li, Aubrey
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