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From: Allen Pais <apais@linux.microsoft.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: "Vinod Koul" <vkoul@kernel.org>,
	"Linus Walleij" <linus.walleij@linaro.org>,
	"Vincent Guittot" <vincent.guittot@linaro.org>,
	olivier.dautricourt@orolia.com, "Stefan Roese" <sr@denx.de>,
	"Kees Cook" <keescook@chromium.org>,
	linux-hardening@vger.kernel.org,
	"Ludovic Desroches" <ludovic.desroches@microchip.com>,
	"Tudor Ambarus" <tudor.ambarus@microchip.com>,
	"Florian Fainelli" <f.fainelli@gmail.com>,
	"Ray Jui" <rjui@broadcom.com>,
	"Scott Branden" <sbranden@broadcom.com>,
	bcm-kernel-feedback-list <bcm-kernel-feedback-list@broadcom.com>,
	"Nicolas Saenz Julienne" <nsaenz@kernel.org>,
	"Paul Cercueil" <paul@crapouillou.net>,
	Eugeniy.Paltsev@synopsys.com,
	"Gustavo Pimentel" <gustavo.pimentel@synopsys.com>,
	"Viresh Kumar" <vireshk@kernel.org>,
	"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
	"Leo Li" <leoyang.li@nxp.com>,
	zw@zh-kernel.org, "Zhou Wang" <wangzhou1@hisilicon.com>,
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	"Sascha Hauer" <s.hauer@pengutronix.de>,
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	"Andreas Färber" <afaerber@suse.de>,
	"Manivannan Sadhasivam" <mani@kernel.org>,
	"Logan Gunthorpe" <logang@deltatee.com>,
	"Sanjay R Mehta" <sanju.mehta@amd.com>,
	"Daniel Mack" <daniel@zonque.org>,
	"Haojian Zhuang" <haojian.zhuang@gmail.com>,
	"Robert Jarzmik" <robert.jarzmik@free.fr>,
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	"Krzysztof Kozlowski" <krzysztof.kozlowski@linaro.org>,
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	"Chen-Yu Tsai" <wens@csie.org>,
	"Jernej Škrabec" <jernej.skrabec@gmail.com>,
	"Samuel Holland" <samuel@sholland.org>,
	dmaengine@vger.kernel.org,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC 1/1] drivers/dma/*: replace tasklets with workqueue
Date: Tue, 31 May 2022 11:19:49 -0700	[thread overview]
Message-ID: <708F627F-0F7D-477F-BDF7-274424501DA0@linux.microsoft.com> (raw)
In-Reply-To: <CAK8P3a3vf_huJ5ysBvFDV=11E-=OxFGiDQ9ND04YKug8g6jV_A@mail.gmail.com>


> 
> [note: something is wrong with your email client, your previous reply appears to
> be in HTML]
> 
  Sorry, fixed it.

>>> That is a good idea, lot of drivers are waiting for completion which can
>>> be signalled from hardirq, this would also reduce the hops we have and
>>> help improve latency a bit. On the downside, some controllers provide
>>> error information, which would need to be dealt with.
>> 
>> 
>>   I am not an expert in dma subsystem, but by using completion from
>> Hardirq context be a concern? Especially with latency.
> 
> I don't see how: to the task waiting for the completion, there should
> be no difference, and for the irq handler sending it, it just avoids
> a few cycles going into softirq context.

  Thanks for clarification. 

  If I have understood it correctly, your suggestion is to move the current
Callback mechanism out to dmaengine as a generic helper function
And introduce completion in dma_async_tx_descriptor to handle what
Tasklets currently do.

Thanks.

> 
>>> Yes that would be a very reasonable mechanism, thanks for the
>>> suggestions.
>> 
>>  I have started working on the idea of global softirq. A RFC should be ready
>> For review soon.
> 
> Ok, thanks!
> 
>       Arnd


  reply	other threads:[~2022-05-31 18:20 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-19 21:16 [RFC 0/1] refactor all tasklet users into other APIs Allen Pais
2022-04-19 21:16 ` [RFC 1/1] drivers/dma/*: replace tasklets with workqueue Allen Pais
2022-04-20  2:31   ` Kees Cook
2022-04-22 16:48     ` Allen Pais
2022-04-25 15:06   ` Linus Walleij
2022-04-25 23:59     ` Allen Pais
2022-04-25 15:56   ` Krzysztof Kozlowski
2022-04-25 19:55     ` Gustavo A. R. Silva
2022-04-28  9:29       ` Andy Shevchenko
     [not found]         ` <DA101ED8-F99F-4DCB-9CB7-370A62C44B65@linux.microsoft.com>
2022-05-12 21:54           ` Linus Walleij
2022-05-16 11:40             ` Vinod Koul
2022-04-26  0:04     ` Allen Pais
2022-04-27  2:45   ` Vinod Koul
2022-04-27 15:20     ` Dave Jiang
2022-04-27 15:58       ` Allen Pais
2022-04-27 15:53     ` Allen Pais
2022-05-25  9:24   ` Linus Walleij
2022-05-25  9:52     ` Vincent Guittot
2022-05-25 11:03     ` Arnd Bergmann
2022-05-25 15:14       ` David Laight
     [not found]         ` <6E248F41-6687-4F2B-B847-DB5459BA1344@linux.microsoft.com>
2022-05-25 17:48           ` Arnd Bergmann
2022-05-25 18:04             ` Allen Pais
2022-05-27  8:06       ` Vinod Koul
2022-05-27 10:59         ` Arnd Bergmann
2022-05-31  6:56           ` Vinod Koul
     [not found]             ` <0A9EDEDC-9E6C-47F8-89C0-48DCDD3F9DE3@linux.microsoft.com>
2022-05-31 18:02               ` Arnd Bergmann
2022-05-31 18:19                 ` Allen Pais [this message]
2022-05-31 19:27                   ` Arnd Bergmann

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