Hi Ryan,
Thanks for you review!
On 2024/5/10 17:05, Ryan Roberts wrote:
On 06/05/2024 16:51, Bang Li 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
Given you are implementing update_mmu_tlb_range() in all the arches that
currently override update_mmu_tlb() I wonder if it would be cleaner to remove
update_mmu_tlb() from all those arches, and define generically, removing the
ability for arches to override it:
static inline void update_mmu_tlb(struct vm_area_struct *vma,
unsigned long address, pte_t *ptep)
{
update_mmu_tlb_range(vma, address, ptep, 1);
}
Agreed! Thank you for your suggestion, I will modify it in the next version.
+#ifndef __HAVE_ARCH_UPDATE_MMU_TLB_RANGE
+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
Then you could use the modern override scheme as Lance suggested and you won't
have any confusion with __HAVE_ARCH_UPDATE_MMU_TLB because it won't exist anymore.
Yes, use update_mmu_tlb_range to implement update_mmu_tlb, we only need
to define the update_mmu_tlb_range macro.
+
/*
* 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);
I certainly agree that this will be a useful helper to have. I expect there will
be more users in future.
Thank you for your affirmation. Baolin’s "add mTHP support for anonymous
shmem" series[1] can also use this function to simplify the code.
[1]
https://lore.kernel.org/linux-mm/cover.1714978902.git.baolin.wang@xxxxxxxxxxxxxxxxx/
Thanks,
Bang
goto release;
}
