MIPS: Collect FPU emulator statistics per-CPU.

On SMP systems, the collection of statistics can cause cache line
bouncing in the lines associated with the counters.  Also there are
races incrementing the counters on multiple CPUs.

To fix both problems, we collect the statistics in per-CPU variables,
and add them up in the debugfs read operation.

As a test I ran the LTP float_bessel test on a 12 CPU Octeon system.

Without CONFIG_DEBUG_FS :             2602 seconds.
With CONFIG_DEBUG_FS:                 2640 seconds.
With non-cpu-local atomic statistics: 14569 seconds.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Cc: linux-mips@linux-mips.org
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/mips/math-emu/dsemul.c b/arch/mips/math-emu/dsemul.c
index df7b9d928efc..36d975ae08f8 100644
--- a/arch/mips/math-emu/dsemul.c
+++ b/arch/mips/math-emu/dsemul.c
@@ -98,7 +98,7 @@ int mips_dsemul(struct pt_regs *regs, mips_instruction ir, unsigned long cpc)
         err |= __put_user(cpc, &fr->epc);
 
         if (unlikely(err)) {
-                fpuemustats.errors++;
+                MIPS_FPU_EMU_INC_STATS(errors);
                 return SIGBUS;
         }
 
@@ -136,7 +136,7 @@ int do_dsemulret(struct pt_regs *xcp)
         err |= __get_user(cookie, &fr->cookie);
 
         if (unlikely(err || (insn != BREAK_MATH) || (cookie != BD_COOKIE))) {
-                fpuemustats.errors++;
+                MIPS_FPU_EMU_INC_STATS(errors);
                 return 0;
         }