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x86, tlb: Switch cr3 in leave_mm() only when needed 

Currently leave_mm() unconditionally switches the cr3 to swapper_pg_dir.
But there is no need to change the cr3, if we already left that mm.

intel_idle() for example calls leave_mm() on every deep c-state entry where
the CPU flushes the TLB for us. Similarly flush_tlb_all() was also calling
leave_mm() whenever the TLB is in LAZY state. Both these paths will be
improved with this change.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1332460885.16101.147.camel@sbsiddha-desk.sc.intel.com
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
hifive-unleashed-5.1
Suresh Siddha 2012-03-22 17:01:25 -07:00 committed by H. Peter Anvin
parent 722bc6b167
commit a6fca40f1d
1 changed files with 5 additions and 3 deletions
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8
arch/x86/mm/tlb.c
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@ -61,11 +61,13 @@ static DEFINE_PER_CPU_READ_MOSTLY(int, tlb_vector_offset);
*/
void leave_mm(int cpu)
{
struct mm_struct *active_mm = percpu_read(cpu_tlbstate.active_mm);
if (percpu_read(cpu_tlbstate.state) == TLBSTATE_OK)
BUG();
cpumask_clear_cpu(cpu,
mm_cpumask(percpu_read(cpu_tlbstate.active_mm)));
load_cr3(swapper_pg_dir);
if (cpumask_test_cpu(cpu, mm_cpumask(active_mm))) {
cpumask_clear_cpu(cpu, mm_cpumask(active_mm));
load_cr3(swapper_pg_dir);
}
}
EXPORT_SYMBOL_GPL(leave_mm);