On 10/15/12 15:00, Hans de Goede wrote: > Hi, > > On 10/15/2012 01:17 PM, Gerd Hoffmann wrote: >> On 10/15/12 12:38, Hans de Goede wrote: >>> Often the guest will queue up new packets in response to a packet, in >>> the >>> async schedule with its IOC flag set, completing. By speeding up the >>> frame-timer, we notice these new packets earlier. This increases the >>> speed (MB/s) of a Linux guest reading from a USB mass storage device >>> by a >>> factor of 1.15 on top of the "Improve latency of interrupt delivery" >>> speed-ups, both with and without input pipelining enabled. >> >> Why not just set async_stepdown to 0? > > We already do that whenever we run a package completion (it get sets when > we move to the executing stage). What this patch does is request the > frame timer to run again in 500 usecs instead of after 1 ms, thus making > us see and process async transfers faster when they are queued up in > response to just completed packages (which we've told the guest about with > the int interrupt). This makes the USB-bus / device idle time between > any 2 transfers of the 3 transfer involving USB storage BOT time shorter, > thereby speeding things up.
Don't feel like having two mechanisms for wakeup rate control. Can't we integrate this with async_stepdown? Changing the baseline maybe, so stepdown=0 doesn't mean 1000 Hz but 2000 Hz? cheers, Gerd
