x86/tlb: add tlb_flushall_shift for specific CPU

Testing show different CPU type(micro architectures and NUMA mode) has
different balance points between the TLB flush all and multiple invlpg.
And there also has cases the tlb flush change has no any help.

This patch give a interface to let x86 vendor developers have a chance
to set different shift for different CPU type.

like some machine in my hands, balance points is 16 entries on
Romely-EP; while it is at 8 entries on Bloomfield NHM-EP; and is 256 on
IVB mobile CPU. but on model 15 core2 Xeon using invlpg has nothing
help.

For untested machine, do a conservative optimization, same as NHM CPU.

Signed-off-by: Alex Shi <alex.shi@intel.com>
Link: http://lkml.kernel.org/r/1340845344-27557-5-git-send-email-alex.shi@intel.com
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 3 insertions, 4 deletions

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 184a02a4d871..2939f2f9edbb 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -316,8 +316,6 @@ void flush_tlb_mm(struct mm_struct *mm)
         preempt_enable();
 }
 
-#define FLUSHALL_BAR    16
-
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static inline unsigned long has_large_page(struct mm_struct *mm,
                                  unsigned long start, unsigned long end)
@@ -352,7 +350,7 @@ void flush_tlb_range(struct vm_area_struct *vma,
 {
         struct mm_struct *mm;
 
-        if (!cpu_has_invlpg || vma->vm_flags & VM_HUGETLB) {
+        if (vma->vm_flags & VM_HUGETLB || tlb_flushall_shift == -1) {
 flush_all:
                 flush_tlb_mm(vma->vm_mm);
                 return;
@@ -373,7 +371,8 @@ flush_all:
                         act_entries = tlb_entries > mm->total_vm ?
                                         mm->total_vm : tlb_entries;
 
-                        if ((end - start)/PAGE_SIZE > act_entries/FLUSHALL_BAR)
+                        if ((end - start) >> PAGE_SHIFT >
+                                        act_entries >> tlb_flushall_shift)
                                 local_flush_tlb();
                         else {
                                 if (has_large_page(mm, start, end)) {