From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Osipenko Subject: Re: [PATCH v4 20/24] PM / devfreq: tegra30: Optimize upper average watermark selection Date: Fri, 19 Jul 2019 20:52:18 +0300 Message-ID: <01b442e4-437d-799d-ed0d-4628bd0d683b@gmail.com> References: <20190707223303.6755-1-digetx@gmail.com> <20190707223303.6755-21-digetx@gmail.com> <20190719045943.73b53e31@dimatab> <1cec80ae-c03e-98a7-1d9f-6b57690610c7@samsung.com> <20190719052111.6641285d@dimatab> <3c9c6a3a-8bce-d304-8472-029e6e673a99@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Chanwoo Choi Cc: Thierry Reding , MyungJoo Ham , Kyungmin Park , Jonathan Hunter , Tomeu Vizoso , linux-pm@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-tegra@vger.kernel.org 19.07.2019 9:11, Chanwoo Choi пишет: > On 19. 7. 19. 오후 3:09, Chanwoo Choi wrote: >> On 19. 7. 19. 오전 11:21, Dmitry Osipenko wrote: >>> В Fri, 19 Jul 2019 11:06:05 +0900 >>> Chanwoo Choi пишет: >>> >>>> On 19. 7. 19. 오전 10:59, Dmitry Osipenko wrote: >>>>> В Fri, 19 Jul 2019 10:36:30 +0900 >>>>> Chanwoo Choi пишет: >>>>> >>>>>> On 19. 7. 8. 오전 7:32, Dmitry Osipenko wrote: >>>>>>> I noticed that CPU may be crossing the dependency threshold very >>>>>>> frequently for some workloads and this results in a lot of >>>>>>> interrupts which could be avoided if MCALL client is keeping >>>>>>> actual EMC frequency at a higher rate. >>>>>>> >>>>>>> Signed-off-by: Dmitry Osipenko >>>>>>> --- >>>>>>> drivers/devfreq/tegra30-devfreq.c | 23 ++++++++++++++++++----- >>>>>>> 1 file changed, 18 insertions(+), 5 deletions(-) >>>>>>> >>>>>>> diff --git a/drivers/devfreq/tegra30-devfreq.c >>>>>>> b/drivers/devfreq/tegra30-devfreq.c index >>>>>>> c3cf87231d25..4d582809acb6 100644 --- >>>>>>> a/drivers/devfreq/tegra30-devfreq.c +++ >>>>>>> b/drivers/devfreq/tegra30-devfreq.c @@ -314,7 +314,8 @@ static >>>>>>> void tegra_actmon_get_lower_upper(struct tegra_devfreq *tegra, } >>>>>>> >>>>>>> static void tegra_devfreq_update_avg_wmark(struct tegra_devfreq >>>>>>> *tegra, >>>>>>> - struct >>>>>>> tegra_devfreq_device *dev) >>>>>>> + struct >>>>>>> tegra_devfreq_device *dev, >>>>>>> + unsigned long freq) >>>>>>> { >>>>>>> unsigned long avg_threshold, lower, upper; >>>>>>> >>>>>>> @@ -323,6 +324,15 @@ static void >>>>>>> tegra_devfreq_update_avg_wmark(struct tegra_devfreq *tegra, >>>>>>> avg_threshold = dev->config->avg_dependency_threshold; >>>>>>> avg_threshold = avg_threshold * ACTMON_SAMPLING_PERIOD; >>>>>>> + /* >>>>>>> + * If cumulative EMC frequency selection is higher than >>>>>>> the >>>>>>> + * device's, then there is no need to set upper watermark >>>>>>> to >>>>>>> + * a lower value because it will result in unnecessary >>>>>>> upper >>>>>>> + * interrupts. >>>>>>> + */ >>>>>>> + if (freq * ACTMON_SAMPLING_PERIOD > upper) >>>>>>> + upper = freq * ACTMON_SAMPLING_PERIOD; >>>>>> >>>>>> Also, 'upper value is used on the patch5. You can combine this code >>>>>> to patch5 or if this patch depends on the cpu notifier, you can >>>>>> combine it to the patch of adding cpu notifier without separate >>>>>> patch. >>>>> >>>>> Well okay, I'll try to squash some of the patches in the next >>>>> revision. Usually I'm receiving comments in the other direction, >>>>> asking to separate patches into smaller changes ;) So that's more a >>>>> personal preference of each maintainer, I'd say. >>>>> >>>> >>>> Right. We have to make the patch with atomic attribute. >>>> But, if there are patches which touch the same code >>>> in the same patchset. We can squash or do refactorig >>>> of this code. >>> >>> The main benefit of having smaller logical changes is that when there is >>> a bug, it's easier to narrow down the offending change using bisection. >>> And it's just easier to review smaller patches, of course. >> >> I agree that the patch should contain the atomic feature. >> To remove the some communication confusion between us, >> I don't mean that you have to merge patches to only one patch. > > If each patch has the atomic attribute, it have to be made as the separate patch. > But, if some patches are included in the the following two case, > can combine patches to one patch. > >> >> It is important to remove the following two cases on the same patchset. >> >> 1. the front patch adds the code and then later patch remove the added code. Okay, I agree that this is applicable to patch #11. >> 2. the front patch changes the code and the later patch again modified >> the changed code of the front patch If patch A adds a new feature and then patch B adds another new feature on top of A, do you consider each of these patches as atomic? [snip]