Messages in this thread | | | Date | Fri, 01 May 2015 16:09:28 +0100 | From | Dietmar Eggemann <> | Subject | Re: [RFCv3 PATCH 37/48] sched: Determine the current sched_group idle-state |
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On 01/05/15 10:56, pang.xunlei@zte.com.cn wrote: > Hi Dietmar, > > Dietmar Eggemann <dietmar.eggemann@arm.com> wrote 2015-05-01 AM 04:17:51: >> >> Re: [RFCv3 PATCH 37/48] sched: Determine the current sched_group > idle-state >> >> On 30/04/15 06:12, pang.xunlei@zte.com.cn wrote: >> > linux-kernel-owner@vger.kernel.org wrote 2015-02-05 AM 02:31:14:
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> Thanks for explaining this in graphic detail. > > From what I understood, let's just assume ARM TC2 has an extra > MC-level C-States SPC(assuming its power is 40 for the big). > > Take the power value from "RFCv3 PATCH 25/48": > static struct idle_state idle_states_cluster_a15[] = { > { .power = 70 }, /* WFI */ > { .power = 25 }, /* cluster-sleep-b */ > }; > > static struct idle_state idle_states_core_a15[] = { > { .power = 0 }, /* WFI */ > }; > > Then we will get the following idle energy table? > static struct idle_state idle_states_core_a15[] = { > { .power = 70 }, /* WFI */ > { .power = 0 }, /* SPC*/ > }; > > static struct idle_state idle_states_cluster_a15[] = { > { .power = 40 }, /* SPC */ > { .power = 25 }, /* cluster-sleep-b */ > }; > > Is this correct?
Yes. It's the same C-state configuration we have on our ARMv8 big.LITTLE JUNO (Cortex A57, A53) board.
# cat /sys/devices/system/cpu/cpu0/cpuidle/state*/name WFI cpu-sleep-0 cluster-sleep-0
> If this is right, there may be a bug. > > For MC-level CPU0: > sg_mask=0x1 sge->nr_idle_states=2 sge->idle_states_below=0 > cpuidle_idx=0 group_idx=1 shallowest_state=1 > > See, group_idle_state() finally returns 1 as CPU0's MC-level > idle engery model index, and this is obviously wrong.
Yes, I can see this problem too.
> So, I think for > "int group_idx = cpuidle_idx - sge->idle_states_below + 1;" > > Maybe we shouldn't add the extra 1 for lowest levels?
Maybe. In any case we will have to resolve this issue in the next version. Thanks for pointing this out!
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