s390/time: use stck clock fast for do_account_vtime

The last high frequency call site of the STCK instruction is
do_account_vtime. Replace it with the faster STCKF instruction.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index 416f2a3..7f0089d 100644 (file)
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -66,7 +66,11 @@ static int do_account_vtime(struct task_struct *tsk, int hardirq_offset)
        clock = S390_lowcore.last_update_clock;
        asm volatile(
                "       stpt    %0\n"   /* Store current cpu timer value */
+#ifdef CONFIG_HAVE_MARCH_Z9_109_FEATURES
+               "       stckf   %1"     /* Store current tod clock value */
+#else
                "       stck    %1"     /* Store current tod clock value */
+#endif
                : "=m" (S390_lowcore.last_update_timer),
                  "=m" (S390_lowcore.last_update_clock));
        S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;