From: David Brownell <david-b@pacbell.net>
To: Paul Walmsley <paul@pwsan.com>
Cc: Russ Dill <russ.dill@gmail.com>,
Artem Bityutskiy <dedekind@yandex.ru>,
David Hagood <david.hagood@gmail.com>,
linux-omap@vger.kernel.org
Subject: Re: Benchmarking: POP flash vs. MMC?
Date: Mon, 6 Apr 2009 03:48:34 -0700 [thread overview]
Message-ID: <200904060348.34996.david-b@pacbell.net> (raw)
In-Reply-To: <alpine.DEB.2.00.0904060433000.22223@utopia.booyaka.com>
On Monday 06 April 2009, Paul Walmsley wrote:
> > Puzzle: get a dma_copypage() to work faster than copy_page().
> > Or a dma_clear_page() faster than clear_page(). Not easy...
>
> Doing it via the DMA engine may save power, since MPU can sleep.
But the CPU overhead of calling the DMA engine can exceed
that of the memcpy()/memset() ... ;)
Another concern is cache impact. In some cases, having the
dirty data in dcache is a big win. With DMA, the cache will
have been purged.
It'd be nice to see DMA versions of this stuff winning;
all I'm saying is that such wins are hard to achieve.
- Dave
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next prev parent reply other threads:[~2009-04-06 10:48 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-03 21:24 Benchmarking: POP flash vs. MMC? david.hagood
2009-04-04 0:57 ` Russ Dill
2009-04-04 2:52 ` David Hagood
2009-04-04 4:16 ` Russ Dill
2009-04-05 22:53 ` David Brownell
2009-04-06 7:41 ` Artem Bityutskiy
2009-04-06 8:13 ` Russ Dill
2009-04-06 9:07 ` Artem Bityutskiy
2009-04-06 9:59 ` David Brownell
2009-04-06 10:08 ` Paul Walmsley
2009-04-06 10:23 ` David Brownell
2009-04-06 10:34 ` Paul Walmsley
2009-04-06 10:48 ` David Brownell [this message]
2009-04-07 17:22 ` Tony Lindgren
2009-04-07 12:09 ` Woodruff, Richard
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