On Wed, 2011-08-31 at 16:21 +0100, Will Deacon wrote: > On Wed, Aug 31, 2011 at 02:43:33PM +0100, Mark Salter wrote: > > On Wed, 2011-08-31 at 09:49 +0100, Will Deacon wrote: > > > On Wed, Aug 31, 2011 at 01:23:47AM +0100, Chen Peter-B29397 wrote: > > > > One question: why this write buffer issue did not happen at UP ARM V7 platform, whose dma buffer > > > > also uncache, but bufferable? > > > > > > Which CPU was on this platform? > > > > Using a 3.1.0-rc4+ kernel on a Pandaboard, and running 'hdparm -t' on a > > usb disk drive, I see ~5.8MB/s read speed. Same kernel, but passing > > nosmp on the commandline, I see 20.3MB/s. > > > > Can someone explain why nosmp would make such a difference? > > Oh gawd, that's horrible. I have a feeling it's probably a separate issue > though, caused by: > > omap_modify_auxcoreboot0(0x200, 0xfffffdff); > > in boot_secondary for OMAP. Unfortunately I have no idea what that line is > doing because it ends up talking to the secure monitor. Okay, I may poke around a bit with that to see I can get a better understanding. With the patched ehci-q.c, I see no noticeable difference between smp and nosmp. Both get me around 23.5MB/s with my setup. --Mark -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
