Messages in this thread | | | Date | Wed, 20 Jun 2018 00:32:14 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [RFC PATCH 1/8] x86/cpufeatures: Enumerate MOVDIRI instruction |
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On Tue, 19 Jun 2018, Fenghua Yu wrote:
> 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.
Makes sense, but why is this not part of the changelog ?
Thanks,
tglx
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