[RFC] count TLB refill for Netlogic XLR chip

[Hillf Danton <dhillf@gmail.com>]

TLB miss is one of the concerned factors when tuning the performance of user
applications, and there are on netlogic XLR chip eight 64-bit registers,
c0 register 22 select 0-7, which could be used as temporary storage.

One of them is used for counting TLB refill, and any comment is appreciated.

Thanks

Signed-off-by: Hillf Danton <dhillf@gmail.com>
---

--- a/arch/mips/mm/tlbex.c      Sat Aug 13 11:44:39 2011
+++ b/arch/mips/mm/tlbex.c      Sat Oct  1 12:41:07 2011
@@ -1239,6 +1239,11 @@ static void __cpuinit build_r4000_tlb_re
        memset(relocs, 0, sizeof(relocs));
        memset(final_handler, 0, sizeof(final_handler));

+       if (current_cpu_type() == CPU_XLR) {
+               UASM_i_MFC0(p, K0, 22, 0);
+               UASM_i_ADDIU(p, K0, K0, 1);
+               UASM_i_MTC0(p, K0, 22, 0);
+       }
        if ((scratch_reg > 0 || scratchpad_available()) && use_bbit_insns()) {
                htlb_info = build_fast_tlb_refill_handler(&p, &l, &r, K0, K1,
                                                          scratch_reg);
--- a/arch/mips/lib/dump_tlb.c  Sat May 14 15:21:02 2011
+++ b/arch/mips/lib/dump_tlb.c  Sat Oct  1 12:46:19 2011
@@ -99,6 +99,10 @@ static void dump_tlb(int first, int last
                               (entrylo1 & 1) ? 1 : 0);
                }
        }
+       if (current_cpu_type() == CPU_XLR) {
+               entrylo0 = __read_64bit_c0_register($22, 0);
+               printk("TLB refill count %llu\n", entrylo0);
+       }
        printk("\n");

        write_c0_entryhi(s_entryhi);