linux-kernel - Re: [PATCH 2/4] mmc: Add virtual command queue support

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Date:   Mon, 9 Sep 2019 15:43:48 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Baolin Wang <baolin.wang@...aro.org>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>, riteshh@...eaurora.org,
        asutoshd@...eaurora.org, Orson Zhai <orsonzhai@...il.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] mmc: Add virtual command queue support

On 9/09/19 3:16 PM, Baolin Wang wrote:
> Hi Adrian,
> 
> On Mon, 9 Sep 2019 at 20:02, Adrian Hunter <adrian.hunter@...el.com> wrote:
>>
>> On 6/09/19 6:52 AM, Baolin Wang wrote:
>>> Now the MMC read/write stack will always wait for previous request is
>>> completed by mmc_blk_rw_wait(), before sending a new request to hardware,
>>> or queue a work to complete request, that will bring context switching
>>> overhead, especially for high I/O per second rates, to affect the IO
>>> performance.
>>>
>>> Thus this patch introduces virtual command queue interface, which is
>>> similar with the hardware command queue engine's idea, that can remove
>>> the context switching.
>>
>> CQHCI is a hardware interface for eMMC's that support command queuing.  What
>> you are doing is a software issue queue, unrelated to CQHCI.  I think you
> 
> Yes.
> 
>> should avoid all reference to CQHCI i.e. call it something else.
> 
> Since its process is similar with CQHCI and re-use the CQHCI's
> interfaces, I called it virtual command queue. I am not sure what else
> name is better, any thoughts? VCQHCI? Thanks.

What about swq for software queue.  Maybe Ulf can suggest something?