Re: [PATCH 1/2] mm/numa: no task_numa_fault() call if page table is changed

From: Zi Yan
Date: Thu Aug 08 2024 - 10:57:50 EST

On 8 Aug 2024, at 10:36, Kefeng Wang wrote:

> On 2024/8/8 22:21, Zi Yan wrote:
>> On 8 Aug 2024, at 10:14, David Hildenbrand wrote:
>>
>>> On 08.08.24 16:13, Zi Yan wrote:
>>>> On 8 Aug 2024, at 4:22, David Hildenbrand wrote:
>>>>
>>>>> On 08.08.24 05:19, Baolin Wang wrote:
>>>>>>
>>>>>>
> ...
>>>>> Agreed, maybe we should simply handle that right away and replace the "goto out;" users by "return 0;".
>>>>>
>>>>> Then, just copy the 3 LOC.
>>>>>
>>>>> For mm/memory.c that would be:
>>>>>
>>>>> diff --git a/mm/memory.c b/mm/memory.c
>>>>> index 67496dc5064f..410ba50ca746 100644
>>>>> --- a/mm/memory.c
>>>>> +++ b/mm/memory.c
>>>>> @@ -5461,7 +5461,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
>>>>> if (unlikely(!pte_same(old_pte, vmf->orig_pte))) {
>>>>> pte_unmap_unlock(vmf->pte, vmf->ptl);
>>>>> - goto out;
>>>>> + return 0;
>>>>> }
>>>>> pte = pte_modify(old_pte, vma->vm_page_prot);
>>>>> @@ -5528,15 +5528,14 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
>>>>> vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
>>>>> vmf->address, &vmf->ptl);
>>>>> if (unlikely(!vmf->pte))
>>>>> - goto out;
>>>>> + return 0;
>>>>> if (unlikely(!pte_same(ptep_get(vmf->pte), vmf->orig_pte))) {
>>>>> pte_unmap_unlock(vmf->pte, vmf->ptl);
>>>>> - goto out;
>>>>> + return 0;
>>>>> }
>>>>> goto out_map;
>>>>> }
>>>>> -out:
>>>>> if (nid != NUMA_NO_NODE)
>>>>> task_numa_fault(last_cpupid, nid, nr_pages, flags);
>>>>> return 0;
>
> Maybe drop this part too,
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 410ba50ca746..07343c1469e0 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -5523,6 +5523,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
> if (!migrate_misplaced_folio(folio, vma, target_nid)) {
> nid = target_nid;
> flags |= TNF_MIGRATED;
> + goto out;
> } else {
> flags |= TNF_MIGRATE_FAIL;
> vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
> @@ -5533,12 +5534,8 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
> pte_unmap_unlock(vmf->pte, vmf->ptl);
> return 0;
> }
> - goto out_map;
> }
>
> - if (nid != NUMA_NO_NODE)
> - task_numa_fault(last_cpupid, nid, nr_pages, flags);
> - return 0;
> out_map:
> /*
> * Make it present again, depending on how arch implements
> @@ -5551,6 +5548,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
> numa_rebuild_single_mapping(vmf, vma, vmf->address, vmf->pte,
> writable);
> pte_unmap_unlock(vmf->pte, vmf->ptl);
> +out:
> if (nid != NUMA_NO_NODE)
> task_numa_fault(last_cpupid, nid, nr_pages, flags);
> return 0;

Even better. Thanks. The updated fixup is attached.



Best Regards,
Yan, Zi
From d761a4bb6cdf3277f1af1d129bf01583962c53b3 Mon Sep 17 00:00:00 2001
From: Zi Yan <ziy@xxxxxxxxxx>
Date: Thu, 8 Aug 2024 10:18:42 -0400
Subject: [PATCH] fixup! mm/numa: no task_numa_fault() call if page table is
changed

---
mm/huge_memory.c | 18 +++++++-----------
mm/memory.c | 19 ++++++++-----------
2 files changed, 15 insertions(+), 22 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index a3c018f2b554..1e22801a9d6e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1681,7 +1681,7 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_same(oldpmd, *vmf->pmd))) {
spin_unlock(vmf->ptl);
- goto out;
+ return 0;
}

pmd = pmd_modify(oldpmd, vma->vm_page_prot);
@@ -1724,23 +1724,16 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
if (!migrate_misplaced_folio(folio, vma, target_nid)) {
flags |= TNF_MIGRATED;
nid = target_nid;
+ goto out:
} else {
flags |= TNF_MIGRATE_FAIL;
vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_same(oldpmd, *vmf->pmd))) {
spin_unlock(vmf->ptl);
- goto out;
+ return 0;
}
- goto out_map;
}

-count_fault:
- if (nid != NUMA_NO_NODE)
- task_numa_fault(last_cpupid, nid, HPAGE_PMD_NR, flags);
-
-out:
- return 0;
-
out_map:
/* Restore the PMD */
pmd = pmd_modify(oldpmd, vma->vm_page_prot);
@@ -1750,7 +1743,10 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
spin_unlock(vmf->ptl);
- goto count_fault;
+out:
+ if (nid != NUMA_NO_NODE)
+ task_numa_fault(last_cpupid, nid, HPAGE_PMD_NR, flags);
+ return 0;
}

/*
diff --git a/mm/memory.c b/mm/memory.c
index 503d493263df..d9b1dff9dc57 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5461,7 +5461,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)

if (unlikely(!pte_same(old_pte, vmf->orig_pte))) {
pte_unmap_unlock(vmf->pte, vmf->ptl);
- goto out;
+ return 0;
}

pte = pte_modify(old_pte, vma->vm_page_prot);
@@ -5523,24 +5523,18 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
if (!migrate_misplaced_folio(folio, vma, target_nid)) {
nid = target_nid;
flags |= TNF_MIGRATED;
+ goto out;
} else {
flags |= TNF_MIGRATE_FAIL;
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
vmf->address, &vmf->ptl);
if (unlikely(!vmf->pte))
- goto out;
+ return 0;
if (unlikely(!pte_same(ptep_get(vmf->pte), vmf->orig_pte))) {
pte_unmap_unlock(vmf->pte, vmf->ptl);
- goto out;
+ return 0;
}
- goto out_map;
}
-
-count_fault:
- if (nid != NUMA_NO_NODE)
- task_numa_fault(last_cpupid, nid, nr_pages, flags);
-out:
- return 0;
out_map:
/*
* Make it present again, depending on how arch implements
@@ -5553,7 +5547,10 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
numa_rebuild_single_mapping(vmf, vma, vmf->address, vmf->pte,
writable);
pte_unmap_unlock(vmf->pte, vmf->ptl);
- goto count_fault;
+out:
+ if (nid != NUMA_NO_NODE)
+ task_numa_fault(last_cpupid, nid, nr_pages, flags);
+ return 0;
}

static inline vm_fault_t create_huge_pmd(struct vm_fault *vmf)
--
2.43.0

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