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SubjectRe: [patch] x86: tlb flush avoid superflous leave_mm()
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On Fri, 2011-09-02 at 15:07 +0800, Shaohua Li wrote:
> If just one page VA tlb is required to be flushed and current task is in lazy
> TLB state, doing leave_mm() is superfluous because it flushes the whole TLB.
> This can reduce some TLB miss.
ping, any comments?

> Signed-off-by: Shaohua Li <shaohua.li@intel.com>
>
> diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
> index d6c0418..3041665 100644
> --- a/arch/x86/mm/tlb.c
> +++ b/arch/x86/mm/tlb.c
> @@ -153,13 +153,13 @@ void smp_invalidate_interrupt(struct pt_regs *regs)
> */
>
> if (f->flush_mm == percpu_read(cpu_tlbstate.active_mm)) {
> - if (percpu_read(cpu_tlbstate.state) == TLBSTATE_OK) {
> - if (f->flush_va == TLB_FLUSH_ALL)
> + if (f->flush_va == TLB_FLUSH_ALL) {
> + if (percpu_read(cpu_tlbstate.state) == TLBSTATE_OK)
> local_flush_tlb();
> else
> - __flush_tlb_one(f->flush_va);
> + leave_mm(cpu);
> } else
> - leave_mm(cpu);
> + __flush_tlb_one(f->flush_va);
> }
> out:
> ack_APIC_irq();
> @@ -306,12 +306,8 @@ void flush_tlb_page(struct vm_area_struct *vma, unsigned long va)
>
> preempt_disable();
>
> - if (current->active_mm == mm) {
> - if (current->mm)
> - __flush_tlb_one(va);
> - else
> - leave_mm(smp_processor_id());
> - }
> + if (current->active_mm == mm)
> + __flush_tlb_one(va);
>
> if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
> flush_tlb_others(mm_cpumask(mm), mm, va);
>




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