Messages in this thread | | | Subject | Re: [RFC 1/2] sched/fair: Fix load_balance() affinity redo path | From | Jeffrey Hugo <> | Date | Thu, 18 May 2017 08:31:55 -0600 |
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On 5/15/2017 8:56 AM, Dietmar Eggemann wrote: > On 12/05/17 21:57, Jeffrey Hugo wrote: >> On 5/12/2017 2:47 PM, Peter Zijlstra wrote: >>> On Fri, May 12, 2017 at 11:01:37AM -0600, Jeffrey Hugo wrote: >>>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >>>> index d711093..8f783ba 100644 >>>> --- a/kernel/sched/fair.c >>>> +++ b/kernel/sched/fair.c >>>> @@ -8219,8 +8219,19 @@ static int load_balance(int this_cpu, struct >>>> rq *this_rq, >>>> /* All tasks on this runqueue were pinned by CPU affinity */ >>>> if (unlikely(env.flags & LBF_ALL_PINNED)) { >>>> + struct cpumask tmp; >>> >>> You cannot have cpumask's on stack. >> >> Well, we need a temp variable to store the intermediate values since the >> cpumask_* operations are somewhat limited, and require a "storage" >> parameter. >> >> Do you have any suggestions to meet all of these requirements? > > What about we use env.dst_grpmask and check if cpus is an improper > subset of env.dst_grpmask? In this case we have to get rid of > setting env.dst_grpmask = NULL in case of CPU_NEWLY_IDLE which is > IMHO not an issue since it's idle is passed via env into > can_migrate_task(). > And cpus has to be and'ed with sched_domain_span(env.sd). > > I'm not sure if this will work with 'not fully connected NUMA' (SD_OVERLAP) > though ...
Hmm. I follow the idea, but I'm not too confident in the SD_OVERLAP case, and looking at your proposed code, it seems invasive to me - changes are needed in what would otherwise be unrelated sections of code. I'd prefer not to go in that direction. Also, it appears that the dst_cpu is still considered as a source for load.
We've got a different idea to address the stack issue, and still keep the change "contained", which I'll roll into a V2 today or tomorrow.
-- Jeffrey Hugo Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
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