Re: [PATCH 2/4] mm: rmap: Allow platforms without mm_cpumask to defer TLB flush
From: Barry Song <hidden>
Date: 2022-07-08 07:00:41
Also in:
linux-doc, linux-mm, lkml
Subsystem:
memory management, memory management - core, memory management - rmap (reverse mapping), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Andrew Morton, David Hildenbrand, Lorenzo Stoakes, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
The cpumask_empty() is indeed just another memory access, which is most likely ok. But wouldn’t adding something like CONFIG_ARCH_HAS_MM_CPUMASK make the code simpler and (slightly, certainly slightly) more performant?
Yep. good suggestion, Nadav. So the code will be as below, right?
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index be0b95e51df6..a91d73866238 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig@@ -81,6 +81,7 @@ config X86 select ARCH_HAS_KCOV if X86_64 select ARCH_HAS_MEM_ENCRYPT select ARCH_HAS_MEMBARRIER_SYNC_CORE + select ARCH_HAS_MM_CPUMASK select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE select ARCH_HAS_PMEM_API if X86_64 select ARCH_HAS_PTE_DEVMAP if X86_64
diff --git a/mm/Kconfig b/mm/Kconfig
index 169e64192e48..7bf54f57ca01 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig@@ -951,6 +951,9 @@ config ARCH_HAS_CURRENT_STACK_POINTER register alias named "current_stack_pointer", this config can be selected. +config ARCH_HAS_MM_CPUMASK + bool + config ARCH_HAS_VM_GET_PAGE_PROT bool
diff --git a/mm/rmap.c b/mm/rmap.c
index 5bcb334cd6f2..13d4f9a1d4f1 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c@@ -692,6 +692,10 @@ static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags) if (!(flags & TTU_BATCH_FLUSH)) return false; +#ifndef CONFIG_ARCH_HAS_MM_CPUMASK + return true; +#endif + /* 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;
Thanks Barry _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel