Messages in this thread Patch in this message | | | Date | Tue, 8 Feb 2022 11:46:45 +0800 | Subject | Re: Re: [PATCH v3] sched/numa: add per-process numa_balancing | From | Gang Li <> |
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On 2022/1/12 22:43, Peter Zijlstra wrote: > On Mon, Dec 06, 2021 at 10:45:28AM +0800, Gang Li wrote: >> This patch add a new api PR_NUMA_BALANCING in prctl. >> >> A large number of page faults will cause performance loss when numa >> balancing is performing. Thus those processes which care about worst-case >> performance need numa balancing disabled. Others, on the contrary, allow a >> temporary performance loss in exchange for higher average performance, so >> enable numa balancing is better for them. >> >> Numa balancing can only be controlled globally by >> /proc/sys/kernel/numa_balancing. Due to the above case, we want to >> disable/enable numa_balancing per-process instead. >> >> Add numa_balancing under mm_struct. Then use it in task_tick_fair. >> >> Set per-process numa balancing: >> prctl(PR_NUMA_BALANCING, PR_SET_NUMAB_DISABLE); //disable >> prctl(PR_NUMA_BALANCING, PR_SET_NUMAB_ENABLE); //enable >> prctl(PR_NUMA_BALANCING, PR_SET_NUMAB_DEFAULT); //follow global > > This seems to imply you can prctl(ENABLE) even if the global is > disabled, IOW sched_numa_balancing is off. >
Of course, this semantic has been discussed here FYI. https://lore.kernel.org/all/20211118085819.GD3301@suse.de/
On 11/18/21 4:58 PM, Mel Gorman wrote: > On Thu, Nov 18, 2021 at 11:26:30AM +0800, Gang Li wrote: >> 3. prctl(PR_NUMA_BALANCING, PR_SET_NUMAB_ENABLE); //enable > > If PR_SET_NUMAB_ENABLE enables numa balancing for a task when > kernel.numa_balancing == 0 instead of returning an error then sure.
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 884f29d07963..2980f33ac61f 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -11169,8 +11169,12 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) >> entity_tick(cfs_rq, se, queued); >> } >> >> - if (static_branch_unlikely(&sched_numa_balancing)) >> +#ifdef CONFIG_NUMA_BALANCING >> + if (curr->mm && (curr->mm->numab_enabled == NUMAB_ENABLED >> + || (static_branch_unlikely(&sched_numa_balancing) >> + && curr->mm->numab_enabled == NUMAB_DEFAULT))) >> task_tick_numa(rq, curr); >> +#endif >> >> update_misfit_status(curr, rq); >> update_overutilized_status(task_rq(curr)); > > There's just about everything wrong there... not least of all the > horrific coding style.
horrible code, yes. I'll do some code clean. -- Thanks Gang Li
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