[PATCH] improve idle cputime accounting

Distinguish the cputime of the idle process where idle is actually using
cpu cycles from the cputime where idle is sleeping on an enabled wait psw.
The former is accounted as system time, the later as idle time.

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

1 files changed, 3 insertions, 61 deletions

diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index 1e06436f07c2..b6110bdf8dc2 100644
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -46,7 +46,6 @@
 #include <asm/processor.h>
 #include <asm/irq.h>
 #include <asm/timer.h>
-#include <asm/cpu.h>
 #include "entry.h"
 
 asmlinkage void ret_from_fork(void) asm ("ret_from_fork");
@@ -76,35 +75,12 @@ unsigned long thread_saved_pc(struct task_struct *tsk)
         return sf->gprs[8];
 }
 
-DEFINE_PER_CPU(struct s390_idle_data, s390_idle) = {
-        .lock = __SPIN_LOCK_UNLOCKED(s390_idle.lock)
-};
-
-void s390_idle_leave(void)
-{
-        struct s390_idle_data *idle;
-        unsigned long long idle_time;
-
-        idle = &__get_cpu_var(s390_idle);
-        idle_time = S390_lowcore.int_clock - idle->idle_enter;
-        spin_lock(&idle->lock);
-        idle->idle_time += idle_time;
-        idle->idle_enter = 0ULL;
-        idle->idle_count++;
-        spin_unlock(&idle->lock);
-        vtime_start_cpu_timer();
-}
-
 extern void s390_handle_mcck(void);
 /*
  * The idle loop on a S390...
  */
 static void default_idle(void)
 {
-        struct s390_idle_data *idle = &__get_cpu_var(s390_idle);
-        unsigned long addr;
-        psw_t psw;
-
         /* CPU is going idle. */
         local_irq_disable();
         if (need_resched()) {
@@ -120,7 +96,6 @@ static void default_idle(void)
         local_mcck_disable();
         if (test_thread_flag(TIF_MCCK_PENDING)) {
                 local_mcck_enable();
-                s390_idle_leave();
                 local_irq_enable();
                 s390_handle_mcck();
                 return;
@@ -128,42 +103,9 @@ static void default_idle(void)
         trace_hardirqs_on();
         /* Don't trace preempt off for idle. */
         stop_critical_timings();
-        vtime_stop_cpu_timer();
-
-        /*
-         * The inline assembly is equivalent to
-         *      idle->idle_enter = get_clock();
-         *      __load_psw_mask(psw_kernel_bits | PSW_MASK_WAIT |
-         *                         PSW_MASK_IO | PSW_MASK_EXT);
-         * The difference is that the inline assembly makes sure that
-         * the stck instruction is right before the lpsw instruction.
-         * This is done to increase the precision.
-         */
-
-        /* Wait for external, I/O or machine check interrupt. */
-        psw.mask = psw_kernel_bits|PSW_MASK_WAIT|PSW_MASK_IO|PSW_MASK_EXT;
-#ifndef __s390x__
-        asm volatile(
-                "       basr    %0,0\n"
-                "0:     ahi     %0,1f-0b\n"
-                "       st      %0,4(%2)\n"
-                "       stck    0(%3)\n"
-                "       lpsw    0(%2)\n"
-                "1:"
-                : "=&d" (addr), "=m" (idle->idle_enter)
-                : "a" (&psw), "a" (&idle->idle_enter), "m" (psw)
-                : "memory", "cc");
-#else /* __s390x__ */
-        asm volatile(
-                "       larl    %0,1f\n"
-                "       stg     %0,8(%2)\n"
-                "       stck    0(%3)\n"
-                "       lpswe   0(%2)\n"
-                "1:"
-                : "=&d" (addr), "=m" (idle->idle_enter)
-                : "a" (&psw), "a" (&idle->idle_enter), "m" (psw)
-                : "memory", "cc");
-#endif /* __s390x__ */
+        /* Stop virtual timer and halt the cpu. */
+        vtime_stop_cpu();
+        /* Reenable preemption tracer. */
         start_critical_timings();
 }