From: Thomas Gleixner <tglx@linutronix.de>
To: Aubrey Li <aubrey.li@intel.com>
Cc: mingo@redhat.com, peterz@infradead.org, hpa@zytor.com,
ak@linux.intel.com, tim.c.chen@linux.intel.com,
dave.hansen@intel.com, arjan@linux.intel.com,
linux-kernel@vger.kernel.org,
Aubrey Li <aubrey.li@linux.intel.com>
Subject: Re: [PATCH v8 1/3] x86/fpu: track AVX-512 usage of tasks
Date: Mon, 11 Feb 2019 14:20:23 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.21.1902111419300.3197@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20190117183822.31333-1-aubrey.li@intel.com>
On Fri, 18 Jan 2019, Aubrey Li wrote:
> User space tools which do automated task placement need information
> about AVX-512 usage of tasks, because AVX-512 usage could cause core
> turbo frequency drop and impact the running task on the sibling CPU.
>
> The XSAVE hardware structure has bits that indicate when valid state
> is present in registers unique to AVX-512 use. Use these bits to
> indicate when AVX-512 has been in use and add per-task AVX-512 state
> timestamp tracking to context switch.
>
> Well-written AVX-512 applications are expected to clear the AVX-512
> state when not actively using AVX-512 registers, so the tracking
> mechanism is imprecise and can theoretically miss AVX-512 usage during
> context switch. But it has been measured to be precise enough to be
> useful under real-world workloads like tensorflow and linpack.
>
> If higher precision is required, suggest user space tools to use the
> PMU-based mechanisms in combination.
>
> Signed-off-by: Aubrey Li <aubrey.li@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
next prev parent reply other threads:[~2019-02-11 13:20 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-17 18:38 [PATCH v8 1/3] x86/fpu: track AVX-512 usage of tasks Aubrey Li
2019-01-17 18:38 ` [PATCH v8 2/3] proc: add AVX-512 usage elapsed time to /proc/pid/status Aubrey Li
2019-02-11 13:26 ` Thomas Gleixner
2019-01-17 18:38 ` [PATCH v8 3/3] Documentation/filesystems/proc.txt: add AVX512_elapsed_ms Aubrey Li
2019-02-01 5:30 ` [PATCH v8 1/3] x86/fpu: track AVX-512 usage of tasks Li, Aubrey
2019-02-11 13:20 ` Thomas Gleixner [this message]
2019-02-11 13:34 ` [tip:x86/fpu] x86/fpu: Track " tip-bot for Aubrey Li
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