linux-kernel - Re: [PATCH v4] mmc: documentation of mmc non-blocking request usage and design.

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Date:	Tue, 5 Jul 2011 16:27:05 -0700
From:	Randy Dunlap <rdunlap@...otime.net>
To:	Per Forlin <per.forlin@...aro.org>
Cc:	linaro-dev@...ts.linaro.org,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-mmc@...r.kernel.org, linux-doc@...r.kernel.org,
	Venkatraman S <svenkatr@...com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Arnd Bergmann <arnd@...db.de>,
	Sourav Poddar <sourav.poddar@...com>,
	Chris Ball <cjb@...top.org>
Subject: Re: [PATCH v4] mmc: documentation of mmc non-blocking request usage
 and design.

On Tue,  5 Jul 2011 23:35:32 +0200 Per Forlin wrote:

> +MMC block driver
> +================
> +
> +The issue_rw_rq() in the MMC block driver is made non-blocking.
> +The increase in throughput is proportional to the time it takes to
> +prepare (major part of preparations are dma_map_sg and dma_unmap_sg)
> +a request and how fast the memory is. The faster the MMC/SD is
> +the more significant the prepare request time becomes. Roughly the expected
> +performance gain is 5% for large writes and 10% on large reads on a L2 cache
> +platform. In power save mode, when clocks run on a lower frequency, the DMA
> +preparation may cost even more. As long as these slower preparations are run
> +in parallel with the transfer performance wont be affected.

                                             won't

Acked-by: Randy Dunlap <rdunlap@...otime.net>


thanks.
---
~Randy
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