On Tue, Oct 29, 2013 at 09:24:05AM -0700, Joe Perches wrote: > On Tue, 2013-10-29 at 09:58 +0100, Markus Pargmann wrote: > > On Tue, Oct 29, 2013 at 01:34:48AM -0700, Joe Perches wrote: > > > On Tue, 2013-10-29 at 09:27 +0100, Markus Pargmann wrote: > > > > This patch speeds up the rx_poll function by reducing the number of > > > > register reads. > > > [] > > > > 125kbit: > > > > Function Hit Time Avg > > > > s^2 > > > > -------- --- ---- --- > > > > --- > > > > c_can_do_rx_poll 63960 10168178 us 158.977 > > > > us 1493056 us > > > > With patch: > > > > c_can_do_rx_poll 63939 4268457 us 66.758 > > > > us 818790.9 us > > > > > > > > 1Mbit: > > > > Function Hit Time Avg > > > > s^2 > > > > -------- --- ---- --- > > > > --- > > > > c_can_do_rx_poll 69489 30049498 us 432.435 > > > > us 9271851 us > > > > With patch: > > > > c_can_do_rx_poll 103034 24220362 us 235.071 > > > > us 6016656 us > [] > > Yes I just measured the timings again: > [] > > ./perf_can_test.sh 125000 30 > [] > > c_can_do_rx_poll 63941 3764057 us 58.867 us > > 776162.2 us > > Good, it's slightly faster still. > > > ./perf_can_test.sh 1000000 30 > [] > > c_can_do_rx_poll 207109 24322185 us 117.436 us > > 171469047 us > [] > > It is interesting that the number of hits for c_can_do_rx_poll is twice as > > much > > as it was with find_next_bit. > > How is this possible? Any idea?
Perhaps the can core received more messages in the previous patch version while being in the poll function. This way it can handle more messages without a new interrupt/poll call. The new patch is faster so it does not receive as many new messages as the old one, leading to more interrupts and less handled messages per poll call. Regards, Markus Pargmann -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
