From mboxrd@z Thu Jan 1 00:00:00 1970 From: Charles Keepax Subject: Re: [PATCH] ASoC: core: Don't schedule DAPM work if already in target state Date: Tue, 28 Aug 2018 11:39:11 +0100 Message-ID: <20180828103911.GX32322@imbe.wolfsonmicro.main> References: <1534520143-29266-1-git-send-email-jonathanh@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1534520143-29266-1-git-send-email-jonathanh@nvidia.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: Jon Hunter Cc: alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, Takashi Iwai , Liam Girdwood , Mark Brown , linux-tegra@vger.kernel.org List-Id: linux-tegra@vger.kernel.org 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 > --- Looks ok to me: Reviewed-by: Charles Keepax Although that said the performance increase is pretty hard to measure on my systems. Thanks, Charles