From: Fenghua Yu <fenghua.yu@intel.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Fenghua Yu <fenghua.yu@intel.com>, Ingo Molnar <mingo@redhat.com>,
H Peter Anvin <hpa@zytor.com>, Ashok Raj <ashok.raj@intel.com>,
Alan Cox <alan@linux.intel.com>,
Ravi V Shankar <ravi.v.shankar@intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>
Subject: Re: [RFC PATCH 1/8] x86/cpufeatures: Enumerate MOVDIRI instruction
Date: Tue, 19 Jun 2018 14:36:44 -0700 [thread overview]
Message-ID: <20180619213644.GC112652@romley-ivt3.sc.intel.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1806191057210.1692@nanos.tec.linutronix.de>
On Tue, Jun 19, 2018 at 10:57:44AM +0200, Thomas Gleixner wrote:
> On Fri, 15 Jun 2018, Fenghua Yu wrote:
>
> > MOVDIRI moves doubleword or quadword from register to memory through
> > direct store which is implemented by using write combining (WC) for
> > writing data directly into memory without caching the data.
>
> And that is useful for what?
Programmable agents can handle streaming offload (e.g. high speed packet
processing in network). Hardware implements a doorbell (tail pointer)
register that is updated by software when adding new work-elements to
the streaming offload work-queue.
MOVDIRI can be used as the doorbell write which is a 4-byte or 8-byte
uncachable write to MMIO. MOVDIRI has lower overhead than other ways
to write the doorbell.
In low latency offload (e.g. Non-Volatile Memory, etc), MOVDIR64B writes
work descriptors (and data in some cases) to device-hosted work-queues
with atomicity.
Thanks.
-Fenghua
next prev parent reply other threads:[~2018-06-19 21:37 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-16 3:06 [RFC PATCH 0/8] x86: Enable a few new instructions Fenghua Yu
2018-06-16 3:06 ` [RFC PATCH 1/8] x86/cpufeatures: Enumerate MOVDIRI instruction Fenghua Yu
2018-06-19 8:57 ` Thomas Gleixner
2018-06-19 21:36 ` Fenghua Yu [this message]
2018-06-19 22:32 ` Thomas Gleixner
2018-06-19 22:35 ` Fenghua Yu
2018-06-25 16:13 ` David Laight
2018-06-16 3:06 ` [RFC PATCH 2/8] x86/cpufeatures: Enumerate MOVDIR64B instruction Fenghua Yu
2018-06-16 3:06 ` [RFC PATCH 3/8] x86/cpufeatures: Enumerate UMONITOR, UMWAIT, and TPAUSE instructions Fenghua Yu
2018-06-16 3:06 ` [RFC PATCH 4/8] cpuidle: Set up maximum umwait time and umwait states Fenghua Yu
2018-06-19 9:03 ` Thomas Gleixner
2018-06-19 15:46 ` Fenghua Yu
2018-06-16 3:06 ` [RFC PATCH 5/8] x86/umwait.c: Add sysfs interface to show tsc_khz Fenghua Yu
2018-06-19 9:08 ` Thomas Gleixner
2018-06-19 15:11 ` Fenghua Yu
2018-06-16 3:06 ` [RFC PATCH 6/8] x86/lib_direct_store.h: Add APIs for direct store instructions Fenghua Yu
2018-06-19 8:47 ` Thomas Gleixner
2018-06-16 3:06 ` [RFC PATCH 7/8] x86/lib_user_wait.h: Add APIs for user wait instructions Fenghua Yu
2018-06-19 9:12 ` Thomas Gleixner
2018-06-19 22:27 ` Fenghua Yu
2018-06-19 22:34 ` Thomas Gleixner
2018-06-19 22:36 ` Fenghua Yu
2018-06-16 3:06 ` [RFC PATCH 8/8] selftests/x86: Self test for the APIs in lib_direct_store.h and lib_user_wait.h Fenghua Yu
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