From ea48761519bd40d7a881c587b5f3177664b2987e Mon Sep 17 00:00:00 2001 From: Venki Pallipadi Date: Wed, 20 Jun 2007 14:26:24 -0700 Subject: [PATCH] [CPUFREQ] ondemand: fix tickless accounting and software coordination bug With tickless kernel and software coordination os P-states, ondemand can look at wrong idle statistics. This can happen when ondemand sampling is happening on CPU 0 and due to software coordination sampling also looks at utilization of CPU 1. If CPU 1 is in tickless state at that moment, its idle statistics will not be uptodate and CPU 0 thinks CPU 1 is idle for less amount of time than it actually is. This can be resolved by looking at all the busy times of CPUs, which is accurate, even with tickless, and use that to determine idle time in a round about way (total time - busy time). Thanks to Arjan for originally reporting the ondemand bug on Lenovo T61. Signed-off-by: Venkatesh Pallipadi Signed-off-by: Dave Jones --- drivers/cpufreq/cpufreq_ondemand.c | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-) diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c index dc6f357..e794527 100644 --- a/drivers/cpufreq/cpufreq_ondemand.c +++ b/drivers/cpufreq/cpufreq_ondemand.c @@ -96,15 +96,25 @@ static struct dbs_tuners { static inline cputime64_t get_cpu_idle_time(unsigned int cpu) { - cputime64_t retval; + cputime64_t idle_time; + cputime64_t cur_jiffies; + cputime64_t busy_time; - retval = cputime64_add(kstat_cpu(cpu).cpustat.idle, - kstat_cpu(cpu).cpustat.iowait); + cur_jiffies = jiffies64_to_cputime64(get_jiffies_64()); + busy_time = cputime64_add(kstat_cpu(cpu).cpustat.user, + kstat_cpu(cpu).cpustat.system); - if (dbs_tuners_ins.ignore_nice) - retval = cputime64_add(retval, kstat_cpu(cpu).cpustat.nice); + busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.irq); + busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.softirq); + busy_time = cputime64_add(busy_time, kstat_cpu(cpu).cpustat.steal); - return retval; + if (!dbs_tuners_ins.ignore_nice) { + busy_time = cputime64_add(busy_time, + kstat_cpu(cpu).cpustat.nice); + } + + idle_time = cputime64_sub(cur_jiffies, busy_time); + return idle_time; } /* @@ -339,7 +349,8 @@ static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info) cur_jiffies = jiffies64_to_cputime64(get_jiffies_64()); total_ticks = (unsigned int) cputime64_sub(cur_jiffies, this_dbs_info->prev_cpu_wall); - this_dbs_info->prev_cpu_wall = cur_jiffies; + this_dbs_info->prev_cpu_wall = get_jiffies_64(); + if (!total_ticks) return; /* -- 2.7.4