From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Brownell Subject: Re: Benchmarking: POP flash vs. MMC? Date: Mon, 6 Apr 2009 03:48:34 -0700 Message-ID: <200904060348.34996.david-b@pacbell.net> References: <6541c55b1b4ad133498add734c9eecc8.squirrel@localhost> <200904060323.21127.david-b@pacbell.net> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from n25.bullet.mail.mud.yahoo.com ([68.142.206.220]:42045 "HELO n25.bullet.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754419AbZDFKsj (ORCPT ); Mon, 6 Apr 2009 06:48:39 -0400 In-Reply-To: Content-Disposition: inline Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Paul Walmsley Cc: Russ Dill , Artem Bityutskiy , David Hagood , linux-omap@vger.kernel.org On Monday 06 April 2009, Paul Walmsley wrote: > > Puzzle: =A0get a dma_copypage() to work faster than copy_page(). > > Or a dma_clear_page() faster than clear_page(). =A0Not easy... >=20 > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html