On Saturday 07 May 2011, Per Forlin wrote: > > The mmc queue never runs empty until end of transfer.. The requests > > are 128 blocks (64k limit set in mmc host driver) compared to 256 > > blocks before. This will not improve performance much since the > > transfer now are smaller than before. The latency is minimal but > > instead there extra number of transfer cause more mmc cmd overhead. > > I added prints to print the wait time in lock_page_killable too. > > I wonder if I can achieve a none empty mmc block queue without > > compromising the mmc host driver performance. > > > There is actually a performance increase from 16.5 MB/s to 18.4 MB/s > when lowering the max_req_size to 64k. > I run a dd test on a pandaboard using 2.6.39-rc5 kernel. I've noticed with a number of cards that using 64k writes is faster than any other size. What I could not figure out yet is whether this is a common hardware optimization for MS Windows (which always uses 64K I/O when it can), or if it's a software effect and we can actually make it go faster with Linux by tuning for other sizes. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
