src/patches/suse-2.6.27.25/patches.arch/ia64-smp_flush_tlb_mm-IPI-fix

   1 From: Dimitri Sivanich <sivanich@sgi.com>
   2 Date: Wed, 15 Apr 2009 15:56:25 +0000 (-0500)
   3 Subject: ia64: smp_flush_tlb_mm() should only send IPI's to cpus in cpu_vm_mask
   4 Patch-mainline: 2.6.30-rc3
   5 Git-commit: edb91dc01a216e84b78721b71a06db1e0db141b7
   6 References: bnc#497807
   7
   8 [IA64] smp_flush_tlb_mm() should only send IPI's to cpus in cpu_vm_mask
   9
  10 Having flush_tlb_mm->smp_flush_tlb_mm() send an IPI to every cpu
  11 on the system is occasionally triggering spin_lock contention in
  12 generic_smp_call_function_interrupt().
  13
  14 Follow x86 arch's lead and only sends IPIs to the cpus in mm->cpu_vm_mask.
  15
  16 Experiments with this change have shown significant improvement in this
  17 contention issue.
  18
  19 Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
  20 Signed-off-by: Tony Luck <tony.luck@intel.com>
  21 Acked-by: Jeff Mahoney <jeffm@suse.com>
  22 ---
  23
  24  arch/ia64/kernel/smp.c |   13 +++++--------
  25  1 file changed, 5 insertions(+), 8 deletions(-)
  26
  27 --- a/arch/ia64/kernel/smp.c
  28 +++ b/arch/ia64/kernel/smp.c
  29 @@ -300,15 +300,12 @@ smp_flush_tlb_mm (struct mm_struct *mm)
  30                 return;
  31         }
  32
  33 +       smp_call_function_mask(mm->cpu_vm_mask,
  34 +               (void (*)(void *))local_finish_flush_tlb_mm, mm, 1);
  35 +       local_irq_disable();
  36 +       local_finish_flush_tlb_mm(mm);
  37 +       local_irq_enable();
  38         preempt_enable();
  39 -       /*
  40 -        * We could optimize this further by using mm->cpu_vm_mask to track which CPUs
  41 -        * have been running in the address space.  It's not clear that this is worth the
  42 -        * trouble though: to avoid races, we have to raise the IPI on the target CPU
  43 -        * anyhow, and once a CPU is interrupted, the cost of local_flush_tlb_all() is
  44 -        * rather trivial.
  45 -        */
  46 -       on_each_cpu((void (*)(void *))local_finish_flush_tlb_mm, mm, 1);
  47  }
  48
  49  void arch_send_call_function_single_ipi(int cpu)