Hi Paul, Good to see you're still hanging around. On 10/5/2015 3:38 PM, Paul Zimmerman wrote: > On Mon, 5 Oct 2015, Alan Stern wrote: >> On Mon, 5 Oct 2015, Paul Jones wrote: >> >>>> Increasing the max_sectors_kb value, on the other hand, might remove >>>> overhead by allowing a higher percentage of the transfer to consist of >>>> real data as opposed to CBW and CSW packets. This depends to some >>>> extent on other factors (such as whether the memory pages are >>>> contiguous, allowing for larger transfers), but it can't hurt. >>> >>> I tried changing the max_sectors_kb to 64 with 64k block size in dd and it’s transferring at the same \ >> speed. >> >> That's a decrease, not an increase. Try changing it to 1024 or more. >> >>> I verified using usbmon and it then indeed requests 64k in each request. >>> Increasing the dd block size to 240k doesn’t change the transfer speed either, and it keeps using \ >>> alternating 120k/8k requests. Increasing the dd block size to 1M doesn’t change the transfer speed \ >>> either, although I get sequences of 2x 120k followed by 1x 16k requests. >> >> The dd block size makes no difference at all, because the kernel >> aggregates the requests from dd. > > In my experience, you need to do at least the following to get max > performance from the mass storage gadget: > > - Use Windows 8 or higher on the host. It's much faster than Linux. > - Put the backing file for the mass storage gadget on a tmpfs. > - Increase FSG_BUFLEN (in Speaking of which... I found this old patch to set the FSG_BUFLEN. Any idea why it never got merged? http://marc.info/?l=linux-usb&m=138722294117498&w=2 Regards, John -- 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
