Re: [PATCH v2 5/5] mm: Add update_mmu_tlb_range()

From: Bang Li
Date: Mon May 06 2024 - 23:26:36 EST


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@xxxxxxxxxxxx> 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@xxxxxxxxxxxx>
---
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