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Date: Fri, 14 Jul 2006 17:42:04 -0500 From: "art" <art@...ltd.com> To: linux-kernel@...r.kernel.org Cc: venkatesh.pallipadi@...el.com, alexey.y.starikovskiy@...el.com, torvalds@...l.org, akpm@...l.org, mingo@...e.hu Subject: cpufreq_ondemand governor - problem problem: on dualcore AMD - if you use cpufreq_ondemand governor and your program is one_process/one_thread intensive one core is busy and second is doing nothing - governor is droping speed on both cores to lowest speed - slowing down busy core process - my dualcore-AMD do this i'm not shure if it is only AMD or INTEL problem too to test this set ondemand governor # echo "ondemand" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor now start in terminal-1 #awk 'BEGIN {for(i=0;i<100000;i++)for(j=0;j<100000;j++);}' observe cpu speed and utilization core1 - utilization 100% speed lowest possible core2 - utilization 0% speed lowest possible now start in terminal-2 #awk 'BEGIN {for(i=0;i<100000;i++)for(j=0;j<100000;j++);}' observe cpu speed and utilization core1 - utilization 100% speed max possible core2 - utilization 100% speed max possible now kill one awk observe cpu speed and utilization core1 - utilization 100% speed lowest possible core2 - utilization 0% speed lowest possible looks like cpufreq ondemand governor sets two frequency dependent cores to speed level ok for that one with lowest utilization slowing down process/thread working on other core. For now it is ok for independent multiprocessor bad for multicore-freq-dependent. temporary dirty patch works for me - your result my vary (for shure it will not work for multi-processor/dualcore - we need identify and pair cores to do same thing) --- cpufreq_ondemand.c-org 2006-07-05 23:09:49.000000000 -0500 +++ cpufreq_ondemand.c 2006-07-14 15:50:56.000000000 -0500 @@ -39,6 +39,7 @@ * All times here are in uS. */ static unsigned int def_sampling_rate; +static unsigned int load_max_core=0; #define MIN_SAMPLING_RATE_RATIO (2) /* for correct statistics, we need at least 10 ticks between each measure */ #define MIN_STAT_SAMPLING_RATE (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10)) @@ -268,6 +269,8 @@ static void dbs_check_cpu(struct cpu_dbs idle_ticks = tmp_idle_ticks; } load = (100 * (total_ticks - idle_ticks)) / total_ticks; + if (load_max_core > load) + load = load_max_core; /* Check for frequency increase */ if (load > dbs_tuners_ins.up_threshold) { @@ -297,6 +300,7 @@ static void dbs_check_cpu(struct cpu_dbs __cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L); } +load_max_core = 0; } static void do_dbs_timer(void *data) --------------------------------------------------- after this patch dualcore-AMD is working OK max speed for 100% utilization on core1 and 0% utilization on core2 xboom art@...ltd.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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