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Message-ID: <6233DD66-9A2E-4885-875D-1E79179146D7@nvidia.com>
Date: Fri, 09 Aug 2024 09:28:09 -0400
From: Zi Yan <ziy@...dia.com>
To: "Huang, Ying" <ying.huang@...el.com>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: Kefeng Wang <wangkefeng.wang@...wei.com>,
David Hildenbrand <david@...hat.com>,
Baolin Wang <baolin.wang@...ux.alibaba.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 1/2] mm/numa: no task_numa_fault() call if page table is
changed
On 9 Aug 2024, at 3:52, Huang, Ying wrote:
> Zi Yan <ziy@...dia.com> writes:
>
>> On 8 Aug 2024, at 21:25, Huang, Ying wrote:
>>
>>> Kefeng Wang <wangkefeng.wang@...wei.com> writes:
>>>
>>>> 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
>>>
>>> IMHO, migration success is normal path, while migration failure is error
>>> processing path. If so, it's better to use "goto" for error processing
>>> instead of normal path.
>>>
>>>> @@ -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;
>>>>
>>>>
>>
>> How about calling task_numa_fault and return in the migration successful path?
>> (target_nid cannot be NUMA_NO_NODE, so if is not needed)
>>
>> diff --git a/mm/memory.c b/mm/memory.c
>> index 3441f60d54ef..abdb73a68b80 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -5526,7 +5526,8 @@ 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;
>> + task_numa_fault(last_cpupid, nid, nr_pages, flags);
>> + return 0;
>> } else {
>> flags |= TNF_MIGRATE_FAIL;
>> vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
>> @@ -5550,7 +5551,6 @@ 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;
>>
>
> This looks better for me, or change it further.
Thanks. Will put a fixup below.
>
> if (migrate_misplaced_folio(folio, vma, target_nid))
> goto out_map_pt;
>
> nid = target_nid;
> flags |= TNF_MIGRATED;
> task_numa_fault(last_cpupid, nid, nr_pages, flags);
>
> return 0;
>
> out_map_pt:
> flags |= TNF_MIGRATE_FAIL;
> vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
> ...
>
I will send a separate patch for this refactoring, since this patch
is meant for fixing commit b99a342d4f11 ("NUMA balancing: reduce TLB flush via delaying mapping on hint page fault”).
Hi Andrew,
Can you fold the fixup below to this patch? Thanks.
From 645fa83b2eed14494755ed67e5c52a55656287ac Mon Sep 17 00:00:00 2001
From: Zi Yan <ziy@...dia.com>
Date: Thu, 8 Aug 2024 22:06:41 -0400
Subject: [PATCH] fixup! fixup! mm/numa: no task_numa_fault() call if page
table is changed
Based on suggestion from Ying.
Link: https://lore.kernel.org/linux-mm/87cymizdvc.fsf@yhuang6-desk2.ccr.corp.intel.com/
Signed-off-by: Zi Yan <ziy@...dia.com>
---
mm/huge_memory.c | 5 +++--
mm/memory.c | 5 +++--
2 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 4e4364a17e6d..0e79ccaaf5e4 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1724,7 +1724,8 @@ 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;
+ task_numa_fault(last_cpupid, nid, HPAGE_PMD_NR, flags);
+ return 0;
} else {
flags |= TNF_MIGRATE_FAIL;
vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
@@ -1743,7 +1744,7 @@ 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);
-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 d9b1dff9dc57..6c3aadf3e5ad 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5523,7 +5523,8 @@ 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;
+ task_numa_fault(last_cpupid, nid, nr_pages, flags);
+ return 0;
} else {
flags |= TNF_MIGRATE_FAIL;
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
@@ -5547,7 +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;
--
2.43.0
Best Regards,
Yan, Zi
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