From a6fca40f1d7f3e232c9de27c1cebbb9f787fbc4f Mon Sep 17 00:00:00 2001 From: Suresh Siddha Date: Thu, 22 Mar 2012 17:01:25 -0700 Subject: [PATCH] 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 Link: http://lkml.kernel.org/r/1332460885.16101.147.camel@sbsiddha-desk.sc.intel.com Signed-off-by: H. Peter Anvin --- arch/x86/mm/tlb.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index d6c0418c3e47..125bcad1b757 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -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);