Excerpts from Peter Zijlstra's message of February 1, 2021 10:09 pm:

On Sat, Jan 30, 2021 at 04:11:23PM -0800, Nadav Amit wrote:

quoted

diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index 427bfcc6cdec..b97136b7010b 100644
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h

@@ -334,8 +334,8 @@ static inline void __tlb_reset_range(struct mmu_gather *tlb)
 
 #ifdef CONFIG_MMU_GATHER_NO_RANGE
 
-#if defined(tlb_flush) || defined(tlb_start_vma) || defined(tlb_end_vma)
-#error MMU_GATHER_NO_RANGE relies on default tlb_flush(), tlb_start_vma() and tlb_end_vma()
+#if defined(tlb_flush)
+#error MMU_GATHER_NO_RANGE relies on default tlb_flush()
 #endif
 
 /*

@@ -362,10 +362,6 @@ static inline void tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vm
 
 #ifndef tlb_flush
 
-#if defined(tlb_start_vma) || defined(tlb_end_vma)
-#error Default tlb_flush() relies on default tlb_start_vma() and tlb_end_vma()
-#endif

#ifdef CONFIG_ARCH_WANT_AGGRESSIVE_TLB_FLUSH_BATCHING
#error ....
#endif

goes here...

quoted

 static inline void tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
 {
 	if (tlb->fullmm)
 		return;
 
+	if (IS_ENABLED(CONFIG_ARCH_WANT_AGGRESSIVE_TLB_FLUSH_BATCHING))
+		return;

Also, can you please stick to the CONFIG_MMU_GATHER_* namespace?

I also don't think AGRESSIVE_FLUSH_BATCHING quite captures what it does.
How about:

	CONFIG_MMU_GATHER_NO_PER_VMA_FLUSH

Yes please, have to have descriptive names.

I didn't quite see why this was much of an improvement though. Maybe 
follow up patches take advantage of it? I didn't see how they all fit 
together.

Thanks,
Nick