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

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