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From: hch@lst.de (Christoph Hellwig)
Subject: [PATCH 4/4] nvme-core: support traffic based keep-alive based on controller support
Date: Fri, 19 Oct 2018 08:00:49 +0200	[thread overview]
Message-ID: <20181019060049.GA27902@lst.de> (raw)
In-Reply-To: <2e1cba3c-a391-8c45-5987-0ba5317a6a19@grimberg.me>

On Thu, Oct 18, 2018@05:38:29PM -0700, Sagi Grimberg wrote:
>
>>> +	nvme_req(req)->ctrl->comp_seen = true;
>>
>> shouldn't we only do this for controllers with keep a live support?
>
> What is the harm setting it anyways? Would it be better to condition it
> on keep alive support instead?

This writes to a cache line in the controller on every I/O completion.
And while it isn't an atomic it isn't exactly going to help scalability,
so I'd rather have a branch before it, which will be predicted not taken
for controllers that don't have the feature (aka at least every PCIe
controller on the planet)

  reply	other threads:[~2018-10-19  6:00 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-28  1:15 [PATCH 0/4] traffic based keep alive support (TP 4024) Sagi Grimberg
2018-09-28  1:15 ` [PATCH 1/4] nvme: introduce ctrl attributes enumeration Sagi Grimberg
2018-09-28  1:15 ` [PATCH 2/4] nvmet: support for traffic based keep-alive Sagi Grimberg
2018-09-28  1:15 ` [PATCH 3/4] nvme-core: cache controller attributes Sagi Grimberg
2018-09-28  1:15 ` [PATCH 4/4] nvme-core: support traffic based keep-alive based on controller support Sagi Grimberg
2018-10-17  7:05   ` Christoph Hellwig
2018-10-19  0:38     ` Sagi Grimberg
2018-10-19  6:00       ` Christoph Hellwig [this message]
2018-10-19  6:30         ` Sagi Grimberg
2018-10-16  1:07 ` [PATCH 0/4] traffic based keep alive support (TP 4024) Sagi Grimberg

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