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 Signed-off-by: Greg Kroah-Hartman Signed-off-by: Willy Tarreau --- drivers/cpufreq/cpufreq_ondemand.c | 25 ++++++++++++++++++------- 1 files changed, 18 insertions(+), 7 deletions(-) diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c index f697449..3bfaeb5 100644 --- a/drivers/cpufreq/cpufreq_ondemand.c +++ b/drivers/cpufreq/cpufreq_ondemand.c @@ -95,15 +95,25 @@ 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; } /* @@ -338,7 +348,8 @@ 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; /* -- 1.5.2.5 -- - 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/