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Date: Sat, 5 Apr 2008 20:10:43 +0530 From: Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com> To: Ken Moffat <zarniwhoop@...world.com> Cc: Ingo Molnar <mingo@...e.hu>, "Rafael J. Wysocki" <rjw@...k.pl>, lkml <linux-kernel@...r.kernel.org>, a.p.zijlstra@...llo.nl, aneesh.kumar@...ux.vnet.ibm.com, dhaval@...ux.vnet.ibm.com, Balbir Singh <balbir@...ibm.com>, skumar@...ux.vnet.ibm.com Subject: Re: Regression in gdm-2.18 since 2.6.24 On Fri, Apr 04, 2008 at 04:32:32PM +0100, Ken Moffat wrote: > > Just to confirm, are you saying you applied patch below on top of > > 2.6.25-rc8 and it solved your shutdown issues? > > > Yes. Thanks for confirming that the patch I sent was what you had tried and found it to fix your problem. That patch however is not something we want to apply for 2.6.25-rc8 (since it will worsen interactivity for other cases). Given that you seem to be seeing the problem even without CONFIG_GROUP_SCHED, only the second hunk of the patch seems to be making a difference for your problem i.e just the hunk below applied on 2.6.25-rc8 (to kernel/sched_fair.c) should fix your problem too: @@ -1145,7 +1145,7 @@ static void check_preempt_wakeup(struct * More easily preempt - nice tasks, while not making * it harder for + nice tasks. */ - if (unlikely(se->load.weight > NICE_0_LOAD)) + if (unlikely(se->load.weight != NICE_0_LOAD)) gran = calc_delta_fair(gran, &se->load); if (pse->vruntime + gran < se->vruntime) [The first hunk is a no-op under !CONFIG_GROUP_SCHED, since entity_is_task() is always 1 for !CONFIG_GROUP_SCHED] This second hunk changes how fast + or - niced tasks get preempted. 2.6.25-rc8 (Bad case): Sets preempt granularity for + niced tasks at 5ms (1 CPU) 2.6.25-rc8 + the hunk above (Good case): Sets preempt granularity for + niced tasks at >5ms So bumping up preempt granularity for + niced tasks seems to make things work for you. IMO the deeper problem lies somewhere else (perhaps is some race issue in gdm itself), which is easily exposed with 2.6.25-rc8 which lets + niced tasks be preempted quickly. To help validate this, can you let us know the result of tuning preempt granularity on native 2.6.25-rc8 (without any patches applied and CONFIG_GROUP_SCHED disabled)? # echo 100000000 > /proc/sys/kernel/sched_wakeup_granularity_ns To check if echo command worked, do: # cat /proc/sys/kernel/sched_wakeup_granularity_ns It should return 100000000. Now try shutting down thr' gdm and pls let me know if it makes a difference. -- Regards, vatsa -- 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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