* Arjan van de Ven <arjan@xxxxxxxxxxxxx> [2008-03-02 11:57:09]: > On Mon, 3 Mar 2008 01:18:13 +0530 > Vaidyanathan Srinivasan <svaidy@xxxxxxxxxxxxxxxxxx> wrote: > > > Hi, > > > > I am trying to play around with the tickless kernel and > > sched_mc_power_savings tunables to increase the idle duration of the > > CPU in an SMP server. sched_mc_power_savings provides good > > consolidation of long running jobs when the system is lightly loaded. > > However I am interested to see CPU idle times for couple minutes on > > atleast few CPUs in an completely idle SMP system. > > > > I have posted related instrumentation results at > > http://lkml.org/lkml/2008/1/8/243 > > > > The experimental setup is identical. Just that I have tried to > > collect more data and also bias the wakeup logic. > > > > The kernel is 2.6.25-rc3 with NO_HZ, SCHED_MC, HIGH_RES_TIMERS, and > > HPET turned on. > > > > I have tried to collect interesting data from tick-sched.c, sched.c > > and softirq.c. > > > > As suggested by Ingo in the previous thread, I have hacked the sched.c > > try_to_wake_up logic so that I can force all wake-ups to happen on > > CPU0. This is just and experiment, in reality we will have to > > carefully choose a domain and CPU to bias all wakeups on an idle > > system. > > > please show us powertop -d output; that way we can at least see sort of what > is going on... I have some more information on the timer interrupt activities in the system. I have obtained the following trace from irq_exit and local timer is the only interrupt on CPUs 1, 2 & 3. Trace CPU/function Timestamp number U2336208 C1 irq_exit EXIT 4452403.687322 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336212 C3 irq_exit EXIT 4452403.722253 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336214 C2 irq_exit EXIT 4452403.722668 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336236 C1 irq_exit EXIT 4452807.345543 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336241 C3 irq_exit EXIT 4452807.381894 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336242 C2 irq_exit EXIT 4452807.382144 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336248 C1 irq_exit EXIT 4453211.003638 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336253 C3 irq_exit EXIT 4453211.041529 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336254 C2 irq_exit EXIT 4453211.041703 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336260 C1 irq_exit EXIT 4453614.662043 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336265 C3 irq_exit EXIT 4453614.701429 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336266 C2 irq_exit EXIT 4453614.701474 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336293 C1 irq_exit EXIT 4454018.320078 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336298 C3 irq_exit EXIT 4454018.361100 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336299 C2 irq_exit EXIT 4454018.361142 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336313 C1 irq_exit EXIT 4454421.978047 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336318 C2 irq_exit EXIT 4454422.020756 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336319 C3 irq_exit EXIT 4454422.020807 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336357 C1 irq_exit EXIT 4454825.636341 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336369 C2 irq_exit EXIT 4454825.681058 ms in_intr 0 in_idle 1 need_resched 0 pid 0 U2336370 C3 irq_exit EXIT 4454825.681191 ms in_intr 0 in_idle 1 need_resched 0 pid 0 This is over a short interval where I complain that the tick is not really getting stopped. Actually there is a pattern of 400ms timer being programmed. Apart from these there are 4ms pattern on one of the CPU that is used to drive tick_sched_timer. Most of the missing trace entries are CPU0 which takes care of all the idle daemon process. There are wakeups due to kondemand and other kernel threads on CPUs 1, 2 & 3, but the time is in seconds. Please help me find the source for this timer. Thanks, Vaidy _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
