Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751709Ab2BYXnS (ORCPT ); Sat, 25 Feb 2012 18:43:18 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:42383 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750843Ab2BYXnQ (ORCPT ); Sat, 25 Feb 2012 18:43:16 -0500 From: "Rafael J. Wysocki" To: Pavel Machek Subject: Re: [RFC PATCH 2/2] CPUfreq ondemand: handle QoS request on DVFS response latency Date: Sun, 26 Feb 2012 00:47:15 +0100 User-Agent: KMail/1.13.6 (Linux/3.3.0-rc5+; KDE/4.6.0; x86_64; ; ) Cc: MyungJoo Ham , cpufreq@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Dave Jones , Len Brown , Kevin Hilman , Jean Pihet , markgross , kyungmin.park@samsung.com, myungjoo.ham@gmail.com References: <1329897815-15871-3-git-send-email-myungjoo.ham@samsung.com> <20120225113005.GC16932@elf.ucw.cz> In-Reply-To: <20120225113005.GC16932@elf.ucw.cz> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201202260047.16127.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6814 Lines: 182 On Saturday, February 25, 2012, Pavel Machek wrote: > On Wed 2012-02-22 17:03:35, MyungJoo Ham wrote: > > With QoS class, DVFS_RESPONSE_LATENCY, users (device drivers and > > userspace processes) may express the desired maximum response latency > > from DVFS mechanisms such as CPUfreq's ondemand governors. Based on such > > QoS requests, the ondemand governor may flexibly adjust sampling rate > > accordingly unless it goes below the min_sampling_rate. > > > > The benefit of having DVFS_RESPONSE_LATENCY is to have faster response > > from user inputs (mouse clicks, keyboard inputs, touchscreen touches, > > and others) without increasing frequency unconditionally. Because some > > input events may not require any performance increases, increasing the > > frequency unconditionally for inputs may simply consume too much energy. > > Adjusting sampling rate based on user inputs enabled to increase > > frequency with less latency if it requires and not to increase frequency > > if it does not require. > > > > Signed-off-by: MyungJoo Ham > > Signed-off-by: Kyungmin Park > > > > -- > > This patch depends on the patch > > "PM / QoS: Introduce new classes: DMA-Throughput and DVFS-Latency". > > and the patch > > "CPUfreq ondemand: update sampling rate without waiting for next > > sampling" > > --- > > drivers/cpufreq/cpufreq_ondemand.c | 108 ++++++++++++++++++++++++++++++++---- > > 1 files changed, 96 insertions(+), 12 deletions(-) > > > > diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c > > index 2d66649..b9188f1 100644 > > --- a/drivers/cpufreq/cpufreq_ondemand.c > > +++ b/drivers/cpufreq/cpufreq_ondemand.c > > @@ -22,6 +22,7 @@ > > #include > > #include > > #include > > +#include > > > > /* > > * dbs is used in this file as a shortform for demandbased switching > > @@ -93,6 +94,7 @@ struct cpu_dbs_info_s { > > * when user is changing the governor or limits. > > */ > > struct mutex timer_mutex; > > + bool activated; /* dbs_timer_init is in effect */ > > }; > > static DEFINE_PER_CPU(struct cpu_dbs_info_s, od_cpu_dbs_info); > > > > @@ -111,6 +113,8 @@ static struct dbs_tuners { > > unsigned int sampling_down_factor; > > unsigned int powersave_bias; > > unsigned int io_is_busy; > > + struct notifier_block dvfs_lat_qos_db; > > + unsigned int dvfs_lat_qos_wants; > > } dbs_tuners_ins = { > > .up_threshold = DEF_FREQUENCY_UP_THRESHOLD, > > .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR, > > @@ -164,6 +168,23 @@ static inline cputime64_t get_cpu_iowait_time(unsigned int cpu, cputime64_t *wal > > } > > > > /* > > + * Find right sampling rate based on sampling_rate and > > + * QoS requests on dvfs latency. > > + */ > > +static unsigned int effective_sampling_rate(void) > > +{ > > + unsigned int effective; > > + > > + if (dbs_tuners_ins.dvfs_lat_qos_wants) > > + effective = min(dbs_tuners_ins.dvfs_lat_qos_wants, > > + dbs_tuners_ins.sampling_rate); > > + else > > + effective = dbs_tuners_ins.sampling_rate; > > + > > + return max(effective, min_sampling_rate); > > +} > > + > > +/* > > * Find right freq to be set now with powersave_bias on. > > * Returns the freq_hi to be used right now and will set freq_hi_jiffies, > > * freq_lo, and freq_lo_jiffies in percpu area for averaging freqs. > > @@ -207,7 +228,7 @@ static unsigned int powersave_bias_target(struct cpufreq_policy *policy, > > dbs_info->freq_lo_jiffies = 0; > > return freq_lo; > > } > > - jiffies_total = usecs_to_jiffies(dbs_tuners_ins.sampling_rate); > > + jiffies_total = usecs_to_jiffies(effective_sampling_rate()); > > jiffies_hi = (freq_avg - freq_lo) * jiffies_total; > > jiffies_hi += ((freq_hi - freq_lo) / 2); > > jiffies_hi /= (freq_hi - freq_lo); > > @@ -259,7 +280,8 @@ show_one(powersave_bias, powersave_bias); > > > > /** > > * update_sampling_rate - update sampling rate effective immediately if needed. > > - * @new_rate: new sampling rate > > + * @new_rate: new sampling rate. if it is 0, regard sampling rate is not > > + * changed and assume that qos request value is changed. > > * > > * If new rate is smaller than the old, simply updaing > > * dbs_tuners_int.sampling_rate might not be appropriate. For example, > > @@ -273,9 +295,13 @@ show_one(powersave_bias, powersave_bias); > > static void update_sampling_rate(unsigned int new_rate) > > { > > int cpu; > > + unsigned int effective; > > + > > + > > + if (new_rate) > > + dbs_tuners_ins.sampling_rate = max(new_rate, min_sampling_rate); > > > > - dbs_tuners_ins.sampling_rate = new_rate > > - = max(new_rate, min_sampling_rate); > > + effective = effective_sampling_rate(); > > > > for_each_online_cpu(cpu) { > > struct cpufreq_policy *policy; > > @@ -283,21 +309,31 @@ static void update_sampling_rate(unsigned int new_rate) > > struct timer_list *timer; > > unsigned long appointed_at; > > > > + /* > > + * mutex_destory(&dbs_info->timer_mutex) should not happen > > + * in this context. > > + */ > > + mutex_lock(&dbs_mutex); > > + > > policy = cpufreq_cpu_get(cpu); > > if (!policy) > > - continue; > > + goto next; > > dbs_info = &per_cpu(od_cpu_dbs_info, policy->cpu); > > cpufreq_cpu_put(policy); > > > > + /* timer_mutex destroyed or will be destoyed soon */ > > + if (!dbs_info->activated) > > + goto next; > > + > > mutex_lock(&dbs_info->timer_mutex); > > > > if (!delayed_work_pending(&dbs_info->work)) > > - goto next; > > + goto next_timer_mutex; > > > > timer = &dbs_info->work.timer; > > appointed_at = timer->expires; > > > > - if (time_before(jiffies + usecs_to_jiffies(new_rate), > > + if (time_before(jiffies + usecs_to_jiffies(effective), > > appointed_at)) { > > > > mutex_unlock(&dbs_info->timer_mutex); > > @@ -305,12 +341,15 @@ static void update_sampling_rate(unsigned int new_rate) > > mutex_lock(&dbs_info->timer_mutex); > > > > schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work, > > - usecs_to_jiffies(new_rate)); > > + usecs_to_jiffies(effective)); > > > > } > > -next: > > +next_timer_mutex: > > mutex_unlock(&dbs_info->timer_mutex); > > +next: > > + mutex_unlock(&dbs_mutex); > > } > > + > > } > > I don't think gotos are helpful here. Can you use normal program > structure or move it to subroutine...? I agree with Pavel that gotos don't make that code particularly clear. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/