lkml.org 
[lkml]   [2013]   [Oct]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2] can: c_can: Speed up rx_poll function
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 |


\
 
 \ /
  Last update: 2013-10-30 09:21    [W:0.043 / U:2.468 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site