Messages in this thread | | | Date | Fri, 21 Jul 2023 23:04:30 +0100 | From | Qais Yousef <> | Subject | Re: [RFC PATCH] sched/fair: Fix impossible migrate_util scenario in load balance |
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On 07/21/23 15:52, Vincent Guittot wrote: > Le vendredi 21 juil. 2023 à 11:57:11 (+0100), Qais Yousef a écrit : > > On 07/20/23 14:31, Vincent Guittot wrote: > > > > > I was trying to reproduce the behavior but I was failing until I > > > realized that this code path is used when the 2 groups are not sharing > > > their cache. Which topology do you use ? I thought that dynamiQ and > > > shares cache between all 8 cpus was the norm for arm64 embedded device > > > now > > > > Hmm good question. phantom domains didn't die which I think is what causing > > this. I can look if this is for a good reason or just historical artifact. > > > > > > > > Also when you say "the little cluster capacity is very small nowadays > > > (around 200 or less)", it is the capacity of 1 core or the cluster ? > > > > I meant one core. So in my case all the littles were busy except for one that > > was mostly idle and never pulled a task from mid where two tasks were stuck on > > a CPU there. And the logs I have added were showing me that the env->imbalance > > was on 150+ range but the task we pull was in the 350+ range. > > I'm not able to reproduce your problem with v6.5-rc2 and without phantom domain, > which is expected because we share cache and weight is 1 so we use the path > > if (busiest->group_weight == 1 || sds->prefer_sibling) { > /* > * When prefer sibling, evenly spread running tasks on > * groups. > */ > env->migration_type = migrate_task; > env->imbalance = sibling_imbalance(env, sds, busiest, local); > } else { >
I missed the deps on topology. So yes you're right, this needs to be addressed first. I seem to remember Sudeep merged some stuff that will flatten these topologies.
Let me chase this topology thing out first.
Thanks!
-- Qais Yousef
> > > > I should have mentioned that I'm on 5.15 - sorry with Android it's hard to run > > mainline on products :( But this code as far as I can tell hasn't changed much. > > > > I can try to find something that runs mainline and reproduce there if you think > > my description of the problem is not clear or applicable. > > > > > > Thanks > > > > -- > > Qais Yousef
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