From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joe Perches Subject: Re: [PATCH v2] can: c_can: Speed up rx_poll function Date: Tue, 29 Oct 2013 09:24:05 -0700 Message-ID: <1383063845.2713.15.camel@joe-AO722> References: <1383035267-19604-1-git-send-email-mpa@pengutronix.de> <1383035688.2713.2.camel@joe-AO722> <20131029085853.GC20839@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: Marc Kleine-Budde , Wolfgang Grandegger , linux-can@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@pengutronix.de To: Markus Pargmann Return-path: In-Reply-To: <20131029085853.GC20839@pengutronix.de> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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?