Re: [RFC PATCH] mm: add last level page table numa info to /proc/pid/numa_pgtable

[haoxin]

在 2022/7/31 上午1:29, Matthew Wilcox 写道:
> On Sun, Jul 31, 2022 at 12:35:28AM +0800, Xin Hao wrote:
> > In many data center servers, the shared memory architectures is
> > Non-Uniform Memory Access (NUMA), remote numa node data access
> > often brings a high latency problem, but what we are easy to ignore
> > is that the page table remote numa access, It can also leads to a
> > performance degradation.
> >
> > So there add a new interface in /proc, This will help developers to
> > get more info about performance issues if they are caused by cross-NUMA.
> Interesting.  The implementation seems rather more complex than
> necessary though.
>
> > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > index 2d04e3470d4c..a51befb47ea8 100644
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -1999,4 +1999,133 @@ const struct file_operations proc_pid_numa_maps_operations = {
> >   	.release	= proc_map_release,
> >   };
> >
> > +struct pgtable_numa_maps {
> > +	unsigned long node[MAX_NUMNODES];
> > +};
> > +
> > +struct pgtable_numa_private {
> > +	struct proc_maps_private proc_maps;
> > +	struct pgtable_numa_maps md;
> > +};
> struct pgtable_numa_private {
> 	struct proc_maps_private proc_maps;
> 	unsigned long node[MAX_NUMNODES];
> };
>
> > +static void gather_pgtable_stats(struct page *page, struct pgtable_numa_maps *md)
> > +{
> > +	md->node[page_to_nid(page)] += 1;
> > +}
> > +
> > +static struct page *can_gather_pgtable_numa_stats(pmd_t pmd, struct vm_area_struct *vma,
> > +		unsigned long addr)
> > +{
> > +	struct page *page;
> > +	int nid;
> > +
> > +	if (!pmd_present(pmd))
> > +		return NULL;
> > +
> > +	if (pmd_huge(pmd))
> > +		return NULL;
> > +
> > +	page = pmd_page(pmd);
> > +	nid = page_to_nid(page);
> > +	if (!node_isset(nid, node_states[N_MEMORY]))
> > +		return NULL;
> > +
> > +	return page;
> > +}
> > +
> > +static int gather_pgtable_numa_stats(pmd_t *pmd, unsigned long addr,
> > +		unsigned long end, struct mm_walk *walk)
> > +{
> > +	struct pgtable_numa_maps *md = walk->private;
> > +	struct vm_area_struct *vma = walk->vma;
> > +	struct page *page;
> > +
> > +	if (pmd_huge(*pmd)) {
> > +		struct page *pmd_page;
> > +
> > +		pmd_page = virt_to_page(pmd);
> > +		if (!pmd_page)
> > +			return 0;
> > +
> > +		if (!node_isset(page_to_nid(pmd_page), node_states[N_MEMORY]))
> > +			return 0;
> > +
> > +		gather_pgtable_stats(pmd_page, md);
> > +		goto out;
> > +	}
> > +
> > +	page = can_gather_pgtable_numa_stats(*pmd, vma, addr);
> > +	if (!page)
> > +		return 0;
> > +
> > +	gather_pgtable_stats(page, md);
> > +
> > +out:
> > +	cond_resched();
> > +	return 0;
> > +}
> static int gather_pgtable_numa_stats(pmd_t *pmd, unsigned long addr,
> 		unsigned long end, struct mm_walk *walk)
> {
> 	struct pgtable_numa_private *priv = walk->private;
> 	struct vm_area_struct *vma = walk->vma;
> 	struct page *page;
> 	int nid;
>
> 	if (pmd_huge(*pmd)) {
> 		page = virt_to_page(pmd);
> 	} else {
> 		page = pmd_page(*pmd);
> 	}
>
> 	nid = page_to_nid(page);
> 	priv->node[nid]++;
>
> 	return 0;
> }
Oh,  Thank you for reviewing the code, i will fix it in the next version.