[PATCH] powerpc/mm: Batch tlb flush when invalidating pte entries

Subsystems: linux for powerpc (32-bit and 64-bit), the rest

STALE3552d

2 messages, 1 author, 2016-11-14 · open the first message on its own page

[PATCH] powerpc/mm: Batch tlb flush when invalidating pte entries

From: Aneesh Kumar K.V <hidden>
Date: 2016-11-14 15:59:17 

This will improve the task exit case, by batching tlb invalidates.

Signed-off-by: Aneesh Kumar K.V <redacted>
---
 arch/powerpc/include/asm/book3s/64/radix.h | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/radix.h b/arch/powerpc/include/asm/book3s/64/radix.h
index aec6e8ee6e27..e8b4f39e9fab 100644
--- a/arch/powerpc/include/asm/book3s/64/radix.h
+++ b/arch/powerpc/include/asm/book3s/64/radix.h
@@ -147,10 +147,16 @@ static inline unsigned long radix__pte_update(struct mm_struct *mm,
 		 * new value of pte
 		 */
 		new_pte = (old_pte | set) & ~clr;
-		psize = radix_get_mmu_psize(pg_sz);
-		radix__flush_tlb_page_psize(mm, addr, psize);
-
-		__radix_pte_update(ptep, 0, new_pte);
+		/*
+		 * If we are trying to clear the pte, we can skip
+		 * the below sequence and batch the tlb flush. The
+		 * tlb flush batching is done by mmu gather code
+		 */
+		if (new_pte) {
+			psize = radix_get_mmu_psize(pg_sz);
+			radix__flush_tlb_page_psize(mm, addr, psize);
+			__radix_pte_update(ptep, 0, new_pte);
+		}
 	} else
 		old_pte = __radix_pte_update(ptep, clr, set);
 	asm volatile("ptesync" : : : "memory");
-- 
2.10.2

Re: [PATCH] powerpc/mm: Batch tlb flush when invalidating pte entries

From: Aneesh Kumar K.V <hidden>
Date: 2016-11-14 16:09:00 

"Aneesh Kumar K.V" [off-list ref] writes:
quoted hunk
This will improve the task exit case, by batching tlb invalidates.

Signed-off-by: Aneesh Kumar K.V <redacted>
---
 arch/powerpc/include/asm/book3s/64/radix.h | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/radix.h b/arch/powerpc/include/asm/book3s/64/radix.h
index aec6e8ee6e27..e8b4f39e9fab 100644
--- a/arch/powerpc/include/asm/book3s/64/radix.h
+++ b/arch/powerpc/include/asm/book3s/64/radix.h
@@ -147,10 +147,16 @@ static inline unsigned long radix__pte_update(struct mm_struct *mm,
 		 * new value of pte
 		 */
 		new_pte = (old_pte | set) & ~clr;
-		psize = radix_get_mmu_psize(pg_sz);
-		radix__flush_tlb_page_psize(mm, addr, psize);
-
-		__radix_pte_update(ptep, 0, new_pte);
+		/*
+		 * If we are trying to clear the pte, we can skip
+		 * the below sequence and batch the tlb flush. The
+		 * tlb flush batching is done by mmu gather code
+		 */
+		if (new_pte) {
+			psize = radix_get_mmu_psize(pg_sz);
+			radix__flush_tlb_page_psize(mm, addr, psize);
+			__radix_pte_update(ptep, 0, new_pte);
+		}
 	} else
 		old_pte = __radix_pte_update(ptep, clr, set);
 	asm volatile("ptesync" : : : "memory");
We can also avoid the ptesync I guess. BTW for transition from V=0 to
a valid pte, we are good without this patch because that is done via set_pte_at()

diff --git a/arch/powerpc/include/asm/book3s/64/radix.h b/arch/powerpc/include/asm/book3s/64/radix.h
index e8b4f39e9fab..83c77323a769 100644
--- a/arch/powerpc/include/asm/book3s/64/radix.h
+++ b/arch/powerpc/include/asm/book3s/64/radix.h
@@ -142,7 +142,6 @@ static inline unsigned long radix__pte_update(struct mm_struct *mm,
 		unsigned long new_pte;
 
 		old_pte = __radix_pte_update(ptep, ~0, 0);
-		asm volatile("ptesync" : : : "memory");
 		/*
 		 * new value of pte
 		 */
@@ -153,6 +152,7 @@ static inline unsigned long radix__pte_update(struct mm_struct *mm,
 		 * tlb flush batching is done by mmu gather code
 		 */
 		if (new_pte) {
+			asm volatile("ptesync" : : : "memory");
 			psize = radix_get_mmu_psize(pg_sz);
 			radix__flush_tlb_page_psize(mm, addr, psize);
 			__radix_pte_update(ptep, 0, new_pte);
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