From mboxrd@z Thu Jan 1 00:00:00 1970 From: joeyli Subject: Re: [PATCH][RFC v2] ACPI: acpi_pad: Do not launch acpi_pad threads on idle cpus Date: Mon, 10 Dec 2018 14:31:53 +0800 Message-ID: <20181210063153.GO5327@linux-l9pv.suse> References: <1525521202-32519-1-git-send-email-yu.c.chen@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1525521202-32519-1-git-send-email-yu.c.chen@intel.com> Sender: linux-kernel-owner@vger.kernel.org To: Chen Yu Cc: "Rafael J. Wysocki" , Len Brown , linux-kernel@vger.kernel.org, Lenny Szubowicz , Jacob Pan , Rui Zhang , linux-acpi@vger.kernel.org List-Id: linux-acpi@vger.kernel.org Hi Chen Yu and ACPI experts, On Sat, May 05, 2018 at 07:53:22PM +0800, Chen Yu wrote: > According to current implementation of acpi_pad driver, > it does not make sense to spawn any power saving threads > on the cpus which are already idle - it might bring > unnecessary overhead on these idle cpus and causes power > waste. So verify the condition that if the number of 'busy' > cpus exceeds the amount of the 'forced idle' cpus is met. > This is applicable due to round-robin attribute of the > power saving threads, otherwise ignore the setting/ACPI > notification. > > Suggested-by: Lenny Szubowicz > Suggested-by: Len Brown > Cc: "Rafael J. Wysocki" > Cc: Lenny Szubowicz > Cc: Len Brown > Cc: Jacob Pan > Cc: Rui Zhang > Cc: linux-acpi@vger.kernel.org > Signed-off-by: Chen Yu Do you have any news for this patch? Why it did not merged by kernel maineline? Thanks a lot! Joey Lee > --- > drivers/acpi/acpi_pad.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 51 insertions(+), 1 deletion(-) > > diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c > index 552c1f7..515e60e 100644 > --- a/drivers/acpi/acpi_pad.c > +++ b/drivers/acpi/acpi_pad.c > @@ -254,12 +254,62 @@ static void set_power_saving_task_num(unsigned int num) > } > } > > +/* > + * Extra acpi_pad threads should not be created until > + * the requested idle count is less than/equals to the > + * number of the busy cpus - it does not make sense to > + * throttle the idle cpus. > + */ > +#define SAMPLE_INTERVAL_JIF 20 > + > +static u64 get_idle_time(int cpu) > +{ > + u64 idle, idle_usecs = -1ULL; > + > + idle_usecs = get_cpu_idle_time_us(cpu, NULL); > + > + if (idle_usecs == -1ULL) > + idle = kcpustat_cpu(cpu).cpustat[CPUTIME_IDLE]; > + else > + idle = idle_usecs * NSEC_PER_USEC; > + > + return idle; > +} > + > +static bool idle_nr_valid(unsigned int num_cpus) > +{ > + int busy_nr = 0, i = 0, load_thresh = 100 - idle_pct; > + > + if (!num_cpus) > + return true; > + > + for_each_online_cpu(i) { > + u64 wall_time, idle_time; > + unsigned int elapsed_delta, idle_delta, load; > + > + wall_time = jiffies64_to_nsecs(get_jiffies_64()); > + idle_time = get_idle_time(i); > + /* Wait and see... */ > + schedule_timeout_uninterruptible(SAMPLE_INTERVAL_JIF); > + > + idle_delta = get_idle_time(i) - idle_time; > + elapsed_delta = jiffies64_to_nsecs(get_jiffies_64()) - wall_time; > + idle_delta = (idle_delta > elapsed_delta) ? elapsed_delta : idle_delta; > + load = 100 * (elapsed_delta - idle_delta) / elapsed_delta; > + if (load >= load_thresh) > + busy_nr++; > + } > + > + return (busy_nr >= num_cpus) ? true : false; > +} > + > static void acpi_pad_idle_cpus(unsigned int num_cpus) > { > get_online_cpus(); > > num_cpus = min_t(unsigned int, num_cpus, num_online_cpus()); > - set_power_saving_task_num(num_cpus); > + if (idle_nr_valid(num_cpus)) > + set_power_saving_task_num(num_cpus); > > put_online_cpus(); > } > -- > 2.7.4 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-acpi" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html