linux-kernel - Re: [PATCH v2 5/5] mm: Add update_mmu_tlb

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Message-ID: <9d251090-ed68-49a2-9e94-7347b71367b3@antgroup.com>
Date: Tue, 07 May 2024 11:26:17 +0800
From: "Bang Li" <libang.li@...group.com>
To: Lance Yang <ioworker0@...il.com>
Cc: akpm@...ux-foundation.org, chenhuacai@...nel.org,
 tsbogend@...ha.franken.de, paul.walmsley@...ive.com, palmer@...belt.com,
 chris@...kel.net, jcmvbkbc@...il.com, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, loongarch@...ts.linux.dev,
 linux-riscv@...ts.infradead.org, david@...hat.com, ryan.roberts@....com,
 libang.linux@...il.com
Subject: Re: [PATCH v2 5/5] mm: Add update_mmu_tlb_range()

Hey Lance,

Thanks for taking time to review!

On 2024/5/7 0:07, Lance Yang wrote:
> On Mon, May 6, 2024 at 11:52 PM Bang Li <libang.li@...group.com> wrote:
>>
>> After the commit 19eaf44954df ("mm: thp: support allocation of anonymous
>> multi-size THP"), it may need to batch update tlb of an address range
>> through the update_mmu_tlb function. We can simplify this operation by
>> adding the update_mmu_tlb_range function, which may also reduce the
>> execution of some unnecessary code in some architectures.
>>
>> Signed-off-by: Bang Li <libang.li@...group.com>
>> ---
>>   include/linux/pgtable.h | 8 ++++++++
>>   mm/memory.c             | 4 +---
>>   2 files changed, 9 insertions(+), 3 deletions(-)
>>
>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
>> index 18019f037bae..869bfe6054f1 100644
>> --- a/include/linux/pgtable.h
>> +++ b/include/linux/pgtable.h
>> @@ -737,6 +737,14 @@ static inline void update_mmu_tlb(struct vm_area_struct *vma,
>>   #define __HAVE_ARCH_UPDATE_MMU_TLB
>>   #endif
>>
>> +#ifndef __HAVE_ARCH_UPDATE_MMU_TLB_RANGE
> 
> IIRC, the contemporary practice is to define a macro with the same name
> as the function if it is being overridden.

The macro __HAVE_ARCH_UPDATE_MMU_TLB_RANGE defined here is aligned with
the macro __HAVE_ARCH_UPDATE_MMU_TLB corresponding to the update_mmu_tlb
function. IMO, it should be better to use my method in this case.

Thanks,
Bang

> 
> Thanks,
> Lance
> 
>> +static inline void update_mmu_tlb_range(struct vm_area_struct *vma,
>> +                               unsigned long address, pte_t *ptep, unsigned int nr)
>> +{
>> +}
>> +#define __HAVE_ARCH_UPDATE_MMU_TLB_RANGE
>> +#endif
>> +
>>   /*
>>    * Some architectures may be able to avoid expensive synchronization
>>    * primitives when modifications are made to PTE's which are already
>> diff --git a/mm/memory.c b/mm/memory.c
>> index eea6e4984eae..2d53e29cf76e 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -4421,7 +4421,6 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
>>          vm_fault_t ret = 0;
>>          int nr_pages = 1;
>>          pte_t entry;
>> -       int i;
>>
>>          /* File mapping without ->vm_ops ? */
>>          if (vma->vm_flags & VM_SHARED)
>> @@ -4491,8 +4490,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
>>                  update_mmu_tlb(vma, addr, vmf->pte);
>>                  goto release;
>>          } else if (nr_pages > 1 && !pte_range_none(vmf->pte, nr_pages)) {
>> -               for (i = 0; i < nr_pages; i++)
>> -                       update_mmu_tlb(vma, addr + PAGE_SIZE * i, vmf->pte + i);
>> +               update_mmu_tlb_range(vma, addr, vmf->pte, nr_pages);
>>                  goto release;
>>          }
>>
>> --
>> 2.19.1.6.gb485710b
>>