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Message-ID: <225de100-6164-47f9-85b3-b191003a8e44@redhat.com>
Date: Tue, 24 Sep 2024 09:40:37 +0200
From: David Hildenbrand <david@...hat.com>
To: Dev Jain <dev.jain@....com>, akpm@...ux-foundation.org,
willy@...radead.org, kirill.shutemov@...ux.intel.com
Cc: ryan.roberts@....com, anshuman.khandual@....com, catalin.marinas@....com,
cl@...two.org, vbabka@...e.cz, mhocko@...e.com, apopple@...dia.com,
dave.hansen@...ux.intel.com, will@...nel.org, baohua@...nel.org,
jack@...e.cz, mark.rutland@....com, hughd@...gle.com,
aneesh.kumar@...nel.org, yang@...amperecomputing.com, peterx@...hat.com,
ioworker0@...il.com, jglisse@...gle.com, wangkefeng.wang@...wei.com,
ziy@...dia.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v4 1/2] mm: Abstract THP allocation
On 24.09.24 06:25, Dev Jain wrote:
>
> On 9/17/24 17:17, David Hildenbrand wrote:
>> On 16.09.24 11:43, Dev Jain wrote:
>>> In preparation for the second patch, abstract away the THP allocation
>>> logic present in the create_huge_pmd() path, which corresponds to the
>>> faulting case when no page is present.
>>>
>>> There should be no functional change as a result of applying this patch,
>>> except that, as David notes at [1], a PMD-aligned address should
>>> be passed to update_mmu_cache_pmd().
>>>
>>> [1]:
>>> https://lore.kernel.org/all/ddd3fcd2-48b3-4170-bcaa-2fe66e093f43@redhat.com/
>>>
>>> Signed-off-by: Dev Jain <dev.jain@....com>
>>> ---
>>> mm/huge_memory.c | 108 +++++++++++++++++++++++++++++------------------
>>> 1 file changed, 66 insertions(+), 42 deletions(-)
>>>
>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>>> index 2a73efea02d7..cdc632b8dc9c 100644
>>> --- a/mm/huge_memory.c
>>> +++ b/mm/huge_memory.c
>>> @@ -1146,47 +1146,88 @@ unsigned long thp_get_unmapped_area(struct
>>> file *filp, unsigned long addr,
>>> }
>>> EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
>>> -static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
>>> - struct page *page, gfp_t gfp)
>>> +static struct folio *vma_alloc_anon_folio_pmd(struct vm_area_struct
>>> *vma,
>>> + unsigned long addr)
>>> {
>>> - struct vm_area_struct *vma = vmf->vma;
>>> - struct folio *folio = page_folio(page);
>>> - pgtable_t pgtable;
>>> - unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
>>> - vm_fault_t ret = 0;
>>> + unsigned long haddr = addr & HPAGE_PMD_MASK;
>>> + gfp_t gfp = vma_thp_gfp_mask(vma);
>>> + const int order = HPAGE_PMD_ORDER;
>>> + struct folio *folio = vma_alloc_folio(gfp, order, vma, haddr,
>>> true);
>>> - VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
>>> + if (unlikely(!folio)) {
>>> + count_vm_event(THP_FAULT_FALLBACK);
>>> + count_mthp_stat(order, MTHP_STAT_ANON_FAULT_FALLBACK);
>>> + goto out;
>>> + }
>>> + VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
>>> if (mem_cgroup_charge(folio, vma->vm_mm, gfp)) {
>>> folio_put(folio);
>>> count_vm_event(THP_FAULT_FALLBACK);
>>> count_vm_event(THP_FAULT_FALLBACK_CHARGE);
>>> - count_mthp_stat(HPAGE_PMD_ORDER,
>>> MTHP_STAT_ANON_FAULT_FALLBACK);
>>> - count_mthp_stat(HPAGE_PMD_ORDER,
>>> MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
>>> - return VM_FAULT_FALLBACK;
>>> + count_mthp_stat(order, MTHP_STAT_ANON_FAULT_FALLBACK);
>>> + count_mthp_stat(order, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
>>> + return NULL;
>>> }
>>> folio_throttle_swaprate(folio, gfp);
>>> - pgtable = pte_alloc_one(vma->vm_mm);
>>> - if (unlikely(!pgtable)) {
>>> - ret = VM_FAULT_OOM;
>>> - goto release;
>>> - }
>>> -
>>> - folio_zero_user(folio, vmf->address);
>>> + folio_zero_user(folio, addr);
>>> /*
>>> * The memory barrier inside __folio_mark_uptodate makes sure that
>>> * folio_zero_user writes become visible before the set_pmd_at()
>>> * write.
>>> */
>>> __folio_mark_uptodate(folio);
>>> +out:
>>> + return folio;
>>> +}
>>> +
>>> +static void __pmd_thp_fault_success_stats(struct vm_area_struct *vma)
>>> +{
>>> + count_vm_event(THP_FAULT_ALLOC);
>>> + count_mthp_stat(HPAGE_PMD_ORDER, MTHP_STAT_ANON_FAULT_ALLOC);
>>> + count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC);
>>> +}
>>
>> just inline that into map_anon_folio_pmd(), please. map_anon_folio_pmd
>> is perfectly readable ;)
>
> If you are asking me to open code it in map_anon_folio_pmd(), I'll do that.
Yes, there will be a single user, so just keep it in the caller.
--
Cheers,
David / dhildenb
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