On Fri, Aug 17, 2018 at 04:35:43PM +0100, Jon Hunter wrote: > When dapm_power_widgets() is called, the dapm_pre_sequence_async() and > dapm_post_sequence_async() functions are scheduled for all DAPM contexts > (apart from the card DAPM context) regardless of whether the DAPM > context is already in the desired state. The overhead of this is not > insignificant and the more DAPM contexts there are the more overhead > there is. > > For example, on the Tegra124 Jetson TK1, when profiling the time taken > to execute the dapm_power_widgets() the following times were observed. > > Times for function dapm_power_widgets() are (us): > Min 23, Ave 190, Max 434, Count 39 > > Here 'Count' is the number of times that dapm_power_widgets() has been > called. Please note that the above time were measured using ktime_get() > to log the time on entry and exit from dapm_power_widgets(). So it > should be noted that these times may not be purely the time take to > execute this function if it is preempted. However, after applying this > patch and measuring the time taken to execute dapm_power_widgets() again > a significant improvement is seen as shown below. > > Times for function dapm_power_widgets() are (us): > Min 4, Ave 16, Max 82, Count 39 > > Therefore, optimise the dapm_power_widgets() function by only scheduling > the dapm_pre/post_sequence_async() work if the DAPM context is not in > the desired state. > > Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx> > --- Looks ok to me: Reviewed-by: Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxx> Although that said the performance increase is pretty hard to measure on my systems. Thanks, Charles _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
