From mboxrd@z Thu Jan 1 00:00:00 1970 From: Artem Bityutskiy Subject: Re: Benchmarking: POP flash vs. MMC? Date: Mon, 06 Apr 2009 10:41:14 +0300 Message-ID: <49D9B21A.2000002@yandex.ru> References: <6541c55b1b4ad133498add734c9eecc8.squirrel@localhost> <1238813563.12072.4.camel@surfer> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from smtp.nokia.com ([192.100.122.230]:25745 "EHLO mgw-mx03.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752677AbZDFHlb (ORCPT ); Mon, 6 Apr 2009 03:41:31 -0400 In-Reply-To: <1238813563.12072.4.camel@surfer> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: David Hagood Cc: Russ Dill , linux-omap@vger.kernel.org David Hagood wrote: > Well, that's not what I would have expected - I would have thought > reads on POP would have been faster than that, and cheaper - the SD > being the same speed but less CPU is surprising. 1. As Russ and David said, OneNAND driver does not really use DMA, because the I/O is done in 2K chunks, and this is just too small piece of data for DMA. 2. UBIFS also compresses data on-the-flight. You may try disabling it and see what changes, but probably not too much, because of the way the driver writes (no DMA). Try mounting with 'compre=3Dnone' option, see here: http://www.linux-mtd.infradead.org/doc/ubifs.html#L_mountopts BTW, some compression testing results may be found here: http://www.linux-mtd.infradead.org/misc/misc.html#L_ubifs_compr although they are not 100% relevant for this case. 3. UBIFS provides you greater data reliability. E.g., it CRCs all data (see here http://www.linux-mtd.infradead.org/doc/ubifs.html#L_checksumming) OneNAND was very reliable last time we tested it, and we disable _some_ CRC checking for it. Try to use the 'no_chk_data_crc' and get better read speed. 4. UBIFS has 'bulk read' feature which works well on OneNAND, (see here: http://www.linux-mtd.infradead.org/doc/ubifs.html#L_readahea= d) Try to enable it as well. You should end up with faster read speed. 5. Last but not least, UBIFS+OneNAND provides just another level of reliability, comparing to SD. In general, SDs are not very good for storing system libraries, etc. I tried to summarize this at some point here: http://www.linux-mtd.infradead.org/doc/ubifs.html#L_raw_vs_ftl HTH. --=20 Best Regards, Artem Bityutskiy (=D0=90=D1=80=D1=82=D1=91=D0=BC =D0=91=D0=B8=D1=82=D1=8E= =D1=86=D0=BA=D0=B8=D0=B9) -- 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