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
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