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Subject[patch] x86: tlb flush avoid superflous leave_mm()
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Date
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.

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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