[v11,1/4] mm/tlbbatch: Introduce arch_tlbbatch_should_defer()

Commit Message

Yicong Yang July 17, 2023, 1:10 p.m. UTC

From: Anshuman Khandual <[e-mail]>

The entire scheme of deferred TLB flush in reclaim path rests on the
fact that the cost to refill TLB entries is less than flushing out
individual entries by sending IPI to remote CPUs. But architecture
can have different ways to evaluate that. Hence apart from checking
TTU_BATCH_FLUSH in the TTU flags, rest of the decision should be
architecture specific.

Signed-off-by: Anshuman Khandual <[e-mail]>
[https://lore.kernel.org/linuxppc-dev/[e-mail]/]
Signed-off-by: Yicong Yang <[e-mail]>
[Rebase and fix incorrect return value type]
Reviewed-by: Kefeng Wang <[e-mail]>
Reviewed-by: Anshuman Khandual <[e-mail]>
Reviewed-by: Barry Song <[e-mail]>
Reviewed-by: Xin Hao <[e-mail]>
Tested-by: Punit Agrawal <[e-mail]>
---
 arch/x86/include/asm/tlbflush.h | 12 ++++++++++++
 mm/rmap.c                       |  9 +--------
 2 files changed, 13 insertions(+), 8 deletions(-)

Comments

Catalin Marinas July 21, 2023, 6:23 p.m. UTC | #1

On Mon, Jul 17, 2023 at 09:10:01PM +0800, Yicong Yang wrote:
> From: Anshuman Khandual <[e-mail]>
> 
> The entire scheme of deferred TLB flush in reclaim path rests on the
> fact that the cost to refill TLB entries is less than flushing out
> individual entries by sending IPI to remote CPUs. But architecture
> can have different ways to evaluate that. Hence apart from checking
> TTU_BATCH_FLUSH in the TTU flags, rest of the decision should be
> architecture specific.
> 
> Signed-off-by: Anshuman Khandual <[e-mail]>
> [https://lore.kernel.org/linuxppc-dev/[e-mail]/]
> Signed-off-by: Yicong Yang <[e-mail]>
> [Rebase and fix incorrect return value type]
> Reviewed-by: Kefeng Wang <[e-mail]>
> Reviewed-by: Anshuman Khandual <[e-mail]>
> Reviewed-by: Barry Song <[e-mail]>
> Reviewed-by: Xin Hao <[e-mail]>
> Tested-by: Punit Agrawal <[e-mail]>

Reviewed-by: Catalin Marinas <[e-mail]>

Patch

diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 80450e1d5385..cf2a1de5d388 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -253,6 +253,18 @@  static inline void flush_tlb_page(struct vm_area_struct *vma, unsigned long a)
 	flush_tlb_mm_range(vma->vm_mm, a, a + PAGE_SIZE, PAGE_SHIFT, false);
 }
 
+static inline bool arch_tlbbatch_should_defer(struct mm_struct *mm)
+{
+	bool should_defer = false;
+
+	/* If remote CPUs need to be flushed then defer batch the flush */
+	if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids)
+		should_defer = true;
+	put_cpu();
+
+	return should_defer;
+}
+
 static inline u64 inc_mm_tlb_gen(struct mm_struct *mm)
 {
 	/*
diff --git a/mm/rmap.c b/mm/rmap.c
index 0c0d8857dfce..6480e526c154 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -688,17 +688,10 @@  static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval)
  */
 static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
 {
-	bool should_defer = false;
-
 	if (!(flags & TTU_BATCH_FLUSH))
 		return false;
 
-	/* If remote CPUs need to be flushed then defer batch the flush */
-	if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids)
-		should_defer = true;
-	put_cpu();
-
-	return should_defer;
+	return arch_tlbbatch_should_defer(mm);
 }
 
 /*