Date: Sat, 5 Mar 2011 13:48:49 +0100 From: Bernd Walter <ticso@cicely7.cicely.de> To: Ian Lepore <freebsd@damnhippie.dyndns.org> Cc: freebsd-arm@freebsd.org Subject: Re: arm/155214: [patch] MMC/SD IO slow on Atmel ARM with modern large SD cards Message-ID: <20110305124849.GW86812@cicely7.cicely.de> In-Reply-To: <201103042020.p24KKBL7007848@freefall.freebsd.org> References: <201103042020.p24KKBL7007848@freefall.freebsd.org>
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On Fri, Mar 04, 2011 at 08:20:11PM +0000, Ian Lepore wrote: > The following reply was made to PR arm/155214; it has been noted by GNATS. > > From: Ian Lepore <freebsd@damnhippie.dyndns.org> > To: ticso@cicely.de > Cc: FreeBSD-gnats-submit@freebsd.org > Subject: Re: arm/155214: [patch] MMC/SD IO slow on Atmel ARM with modern > large SD cards > Date: Fri, 04 Mar 2011 13:10:12 -0700 > > On Thu, 2011-03-03 at 00:52 +0100, Bernd Walter wrote: > > On Wed, Mar 02, 2011 at 02:53:18PM -0700, Ian Lepore wrote: > Since 15mhz/4bit is still twice the data throughput of 30mhz/1bit I > decided to do some crude benchmarking to see if it's worth the trouble > of making 4-bit work correctly. The results appear below. In > summary, there is definitely a benefit to using 4-bit transfers, but > the improvement isn't nearly as dramatic as the change from single- to > multi-block IO. 4bit transport has a more interesting point than bandwidth. An 64k read with 15MHz/1bit will have ~35ms calculated latency just for the data transport, which I consider a pretty high value. Nevertheless I'm still exited about your multiblock support and your measured values already look fantastic. > Based on the benchmark results, and the fact that I don't really have > the time to take on the dev/mmc changes right now, I think we should > adopt the multi-block patches and stick with 30mhz/1-bit for now. I completely agree with you. The main problem was write performance and this is clearly solved to match with media capabilities - not to speak that the former single block writes also had an increased media wear. -- B.Walter <bernd@bwct.de> http://www.bwct.de Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.
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