[IA64] smp_flush_tlb_mm() should only send IPI's to cpus in cpu_vm_mask

Having flush_tlb_mm->smp_flush_tlb_mm() send an IPI to every cpu
on the system is occasionally triggering spin_lock contention in
generic_smp_call_function_interrupt().

Follow x86 arch's lead and only sends IPIs to the cpus in mm->cpu_vm_mask.

Experiments with this change have shown significant improvement in this
contention issue.

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 5 insertions, 8 deletions

diff --git a/arch/ia64/kernel/smp.c b/arch/ia64/kernel/smp.c
index c2d982385dce..5230eaafd83f 100644
--- a/arch/ia64/kernel/smp.c
+++ b/arch/ia64/kernel/smp.c
@@ -301,15 +301,12 @@ smp_flush_tlb_mm (struct mm_struct *mm)
                 return;
         }
 
+        smp_call_function_mask(mm->cpu_vm_mask,
+                (void (*)(void *))local_finish_flush_tlb_mm, mm, 1);
+        local_irq_disable();
+        local_finish_flush_tlb_mm(mm);
+        local_irq_enable();
         preempt_enable();
-        /*
-         * We could optimize this further by using mm->cpu_vm_mask to track which CPUs
-         * have been running in the address space.  It's not clear that this is worth the
-         * trouble though: to avoid races, we have to raise the IPI on the target CPU
-         * anyhow, and once a CPU is interrupted, the cost of local_flush_tlb_all() is
-         * rather trivial.
-         */
-        on_each_cpu((void (*)(void *))local_finish_flush_tlb_mm, mm, 1);
 }
 
 void arch_send_call_function_single_ipi(int cpu)