linux-kernel - Re: [PATCH v2 1/8] mmc: sdhci: Get rid of finish

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Message-ID: <99e1b9cb-8eef-9ef2-4caa-3d5c98e9c6f3@intel.com>
Date:   Tue, 2 Apr 2019 16:12:29 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Faiz Abbas <faiz_abbas@...com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        linux-omap <linux-omap@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, Kishon <kishon@...com>,
        Chunyan Zhang <zhang.chunyan@...aro.org>,
        Grygorii Strashko <grygorii.strashko@...com>
Subject: Re: [PATCH v2 1/8] mmc: sdhci: Get rid of finish_tasklet

On 2/04/19 10:59 AM, Faiz Abbas wrote:
> Hi Adrian,
> 
> On 26/03/19 1:03 PM, Adrian Hunter wrote:
>> On 18/03/19 11:33 AM, Ulf Hansson wrote:
>>> + Arnd, Grygorii
>>>
>>> On Fri, 15 Feb 2019 at 20:17, Faiz Abbas <faiz_abbas@...com> wrote:
>>>>
>>>> sdhci.c has two bottom halves implemented. A threaded_irq for handling
>>>> card insert/remove operations and a tasklet for finishing mmc requests.
>>>> With the addition of external dma support, dmaengine APIs need to
>>>> terminate in non-atomic context before unmapping the dma buffers.
>>>>
>>>> To facilitate this, remove the finish_tasklet and move the call of
>>>> sdhci_request_done() to the threaded_irq() callback. Also move the
>>>> interrupt result variable to sdhci_host so it can be populated from
>>>> anywhere inside the sdhci_irq handler.
>>>>
>>>> Signed-off-by: Faiz Abbas <faiz_abbas@...com>
>>>
>>> Adrian, I think it makes sense to apply this patch, even if there is
>>> very minor negative impact throughput wise.
>>>
>>> To me, it doesn't seems like MMC/SD/SDIO has good justification for
>>> using tasklets, besides from the legacy point of view, of course.
>>> Instead, I think we should try to move all mmc hosts into using
>>> threaded IRQs.
>>>
>>> So, what do you think? Can you overlook the throughput drop and
>>> instead we can try to recover this on top with other optimizations?
>>
>> I tend to favour good results as expressed here:
>>
>> 	https://lkml.org/lkml/2007/6/22/360
>>
>> So I want to do optimization first.
>>
>> But performance is not the only problem with the patch.  Give me a few
>> days and I will see what I can come up with.
>>
> 
> Gentle ping on this.

Working on it :-)