Re: [PATCH v2 2/4] mm: rmap: Allow platforms without mm_cpumask to defer TLB flush
From: Kefeng Wang <hidden>
Date: 2022-07-11 13:35:15
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Hi Barry， On 2022/7/11 11:46, Barry Song wrote:
From: Barry Song <redacted> Platforms like ARM64 have hareware TLB shootdown broadcast. They don't maintain mm_cpumask but just send tlbi and related sync instructions for TLB flush. task's mm_cpumask is normally empty in this case. We also allow deferred TLB flush on this kind of platforms. Signed-off-by: Barry Song <redacted>> ---
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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 booldiff --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 +
Here is another option to enable arch's tlbbatch defer [1] https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20171101101735.2318-2-khandual@linux.vnet.ibm.com/
/* 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;
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