linux-kernel - Re: [RFC PATCH V1 1/1] sched/numa: Enhance vma scanning logic

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Message-ID: <500591b7-9c36-a769-88aa-0f130256ebc9@amd.com>
Date:   Fri, 27 Jan 2023 20:57:55 +0530
From:   Raghavendra K T <raghavendra.kt@....com>
To:     Mel Gorman <mgorman@...e.de>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Bharata B Rao <bharata@....com>,
        Disha Talreja <dishaa.talreja@....com>,
        Mike Rapoport <rppt@...nel.org>
Subject: Re: [RFC PATCH V1 1/1] sched/numa: Enhance vma scanning logic

On 1/27/2023 3:47 PM, Mel Gorman wrote:
> On Wed, Jan 25, 2023 at 12:48:16AM +0530, Raghavendra K T wrote:
>> looks like we have to additionally handle numab initialization in
>> vm_area_dup() code path. something like below fixed it (copied pasted
>> from tty):
>>
> 
> Yep, it wasn't even boot tested. Better approach is something like this,
> still not actually tested
> 
>   include/linux/mm.h       |  9 +++++++++
>   include/linux/mm_types.h |  7 +++++++
>   kernel/fork.c            |  2 ++
>   kernel/sched/fair.c      | 17 +++++++++++++++++
>   4 files changed, 35 insertions(+)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 8f857163ac89..481f90dc1983 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -612,6 +612,14 @@ struct vm_operations_struct {
>   					  unsigned long addr);
>   };
>   
> +#ifdef CONFIG_NUMA_BALANCING
> +#define vma_numab_init(vma) do { (vma)->numab = NULL; } while (0)
> +#define vma_numab_free(vma) do { kfree((vma)->numab); } while (0)
> +#else
> +static inline void vma_numab_init(struct vm_area_struct *vma) {}
> +static inline void vma_numab_free(struct vm_area_struct *vma) {}
> +#endif /* CONFIG_NUMA_BALANCING */
> +
>   static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
>   {
>   	static const struct vm_operations_struct dummy_vm_ops = {};
> @@ -620,6 +628,7 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
>   	vma->vm_mm = mm;
>   	vma->vm_ops = &dummy_vm_ops;
>   	INIT_LIST_HEAD(&vma->anon_vma_chain);
> +	vma_numab_init(vma);
>   }
>   
>   static inline void vma_set_anonymous(struct vm_area_struct *vma)
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 9757067c3053..43ce363d5124 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -526,6 +526,10 @@ struct anon_vma_name {
>   	char name[];
>   };
>   
> +struct vma_numab {
> +	unsigned long next_scan;
> +};
> +
>   /*
>    * This struct describes a virtual memory area. There is one of these
>    * per VM-area/task. A VM area is any part of the process virtual memory
> @@ -593,6 +597,9 @@ struct vm_area_struct {
>   #endif
>   #ifdef CONFIG_NUMA
>   	struct mempolicy *vm_policy;	/* NUMA policy for the VMA */
> +#endif
> +#ifdef CONFIG_NUMA_BALANCING
> +	struct vma_numab *numab;	/* NUMA Balancing state */
>   #endif
>   	struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
>   } __randomize_layout;
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 9f7fe3541897..5a2e8c3cc410 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -474,6 +474,7 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
>   		 */
>   		*new = data_race(*orig);
>   		INIT_LIST_HEAD(&new->anon_vma_chain);
> +		vma_numab_init(new);
>   		dup_anon_vma_name(orig, new);
>   	}
>   	return new;
> @@ -481,6 +482,7 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
>   
>   void vm_area_free(struct vm_area_struct *vma)
>   {
> +	vma_numab_free(vma);
>   	free_anon_vma_name(vma);
>   	kmem_cache_free(vm_area_cachep, vma);
>   }
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index c36aa54ae071..6a1cffdfc76b 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3027,6 +3027,23 @@ static void task_numa_work(struct callback_head *work)
>   		if (!vma_is_accessible(vma))
>   			continue;
>   
> +		/* Initialise new per-VMA NUMAB state. */
> +		if (!vma->numab) {
> +			vma->numab = kzalloc(sizeof(struct vma_numab), GFP_KERNEL);
> +			if (!vma->numab)
> +				continue;
> +
> +			vma->numab->next_scan = now +
> +				msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
> +		}
> +
> +		/*
> +		 * After the first scan is complete, delay the balancing scan
> +		 * for new VMAs.
> +		 */
> +		if (mm->numa_scan_seq && time_before(jiffies, vma->numab->next_scan))
> +			continue;
> +
>   		do {
>   			start = max(start, vma->vm_start);
>   			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);


Thank you Mel. This looks better now.
Yes we would have moved to mm.h eventually to avoid #if clutter.

Also for PATCH2 function common to memory.c and huge_memory.c would
need the same to handle hugetlb vma as suggested by you.
Working on gathering numbers and PID clear logic now. will post V2 soon.

Thanks
- Raghu