On Mon, Apr 6, 2009 at 12:41 AM, Artem Bityutskiy <dedekind@xxxxxxxxx> wrote: > 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. All very relevant, but just to avoid confusion; the tests were performed on a Beagleboard with 256MB of Micron NAND. http://www.micron.com/products/partdetail?part=MT29C2G24MAKLAJG-6 IT Also, it appears from looking an the openzoom git, there are some patches to add DMA support in, but I'm not sure what effect they have. > 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=none' 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_readahead) > 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. > > -- > Best Regards, > Artem Bityutskiy (Артём Битюцкий) > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
