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Message-ID: <a82a7441-3a70-40b6-a765-c91f47bb728c@redhat.com>
Date: Mon, 3 Jun 2024 11:03:55 +0200
From: David Hildenbrand <david@...hat.com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>,
Barry Song <21cnbao@...il.com>, Lance Yang <ioworker0@...il.com>
Cc: akpm@...ux-foundation.org, ryan.roberts@....com, ziy@...dia.com,
fengwei.yin@...el.com, ying.huang@...el.com, libang.li@...group.com,
linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] mm/mlock: implement folio_mlock_step() using
folio_pte_batch()
On 03.06.24 10:58, Baolin Wang wrote:
>
>
> On 2024/6/3 12:14, Barry Song wrote:
>> On Mon, Jun 3, 2024 at 3:31 PM Lance Yang <ioworker0@...il.com> wrote:
>>>
>>> Let's make folio_mlock_step() simply a wrapper around folio_pte_batch(),
>>> which will greatly reduce the cost of ptep_get() when scanning a range of
>>> contptes.
>>>
>>> Signed-off-by: Lance Yang <ioworker0@...il.com>
>>> ---
>>> mm/mlock.c | 23 ++++++-----------------
>>> 1 file changed, 6 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/mm/mlock.c b/mm/mlock.c
>>> index 30b51cdea89d..1ae6232d38cf 100644
>>> --- a/mm/mlock.c
>>> +++ b/mm/mlock.c
>>> @@ -307,26 +307,15 @@ void munlock_folio(struct folio *folio)
>>> static inline unsigned int folio_mlock_step(struct folio *folio,
>>> pte_t *pte, unsigned long addr, unsigned long end)
>>> {
>>> - unsigned int count, i, nr = folio_nr_pages(folio);
>>> - unsigned long pfn = folio_pfn(folio);
>>> - pte_t ptent = ptep_get(pte);
>>> -
>>> - if (!folio_test_large(folio))
>>> + if (likely(!folio_test_large(folio)))
>>> return 1;
>>>
>>> - count = pfn + nr - pte_pfn(ptent);
>>> - count = min_t(unsigned int, count, (end - addr) >> PAGE_SHIFT);
>>> -
>>> - for (i = 0; i < count; i++, pte++) {
>>> - pte_t entry = ptep_get(pte);
>>> -
>>> - if (!pte_present(entry))
>>> - break;
>>> - if (pte_pfn(entry) - pfn >= nr)
>>> - break;
>>> - }
>>> + const fpb_t fpb_flags = FPB_IGNORE_DIRTY | FPB_IGNORE_SOFT_DIRTY;
>>> + int max_nr = (end - addr) / PAGE_SIZE;
>>> + pte_t ptent = ptep_get(pte);
>>>
>>> - return i;
>>> + return folio_pte_batch(folio, addr, pte, ptent, max_nr, fpb_flags, NULL,
>>> + NULL, NULL);
>>> }
>>
>> what about a minimum change as below?
>> index 30b51cdea89d..e8b98f84fbd2 100644
>> --- a/mm/mlock.c
>> +++ b/mm/mlock.c
>> @@ -307,26 +307,15 @@ void munlock_folio(struct folio *folio)
>> static inline unsigned int folio_mlock_step(struct folio *folio,
>> pte_t *pte, unsigned long addr, unsigned long end)
>> {
>> - unsigned int count, i, nr = folio_nr_pages(folio);
>> - unsigned long pfn = folio_pfn(folio);
>> + unsigned int count = (end - addr) >> PAGE_SHIFT;
>> pte_t ptent = ptep_get(pte);
>> + const fpb_t fpb_flags = FPB_IGNORE_DIRTY | FPB_IGNORE_SOFT_DIRTY;
>>
>> if (!folio_test_large(folio))
>> return 1;
>>
>> - count = pfn + nr - pte_pfn(ptent);
>> - count = min_t(unsigned int, count, (end - addr) >> PAGE_SHIFT);
>> -
>> - for (i = 0; i < count; i++, pte++) {
>> - pte_t entry = ptep_get(pte);
>> -
>> - if (!pte_present(entry))
>> - break;
>> - if (pte_pfn(entry) - pfn >= nr)
>> - break;
>> - }
>> -
>> - return i;
>> + return folio_pte_batch(folio, addr, pte, ptent, count, fpb_flags, NULL,
>> + NULL, NULL);
>> }
>
> LGTM.
> Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
>
Acked-by: David Hildenbrand <david@...hat.com>
--
Cheers,
David / dhildenb
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