[S390] boot cputime accounting

Start the cpu time accounting very early to catch the cpu time spent
for the initial kernel setup. To make the output of /proc/uptime
match the sum of all cpu accounting values of the boot cpu reset
xtime and wall_to_monotonic to sane values based on the TOD clock.
The values set by timekeeping_init are off by up to a second.

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

diff --git a/arch/s390/kernel/head.S b/arch/s390/kernel/head.S
index 16f8975..bba1449 100644 (file)
--- a/arch/s390/kernel/head.S
+++ b/arch/s390/kernel/head.S
@@ -473,7 +473,10 @@ startup:basr       %r13,0                  # get base
        xc      0x300(256),0x300
        l       %r1,5f-.LPG0(%r13)
        stck    0(%r1)
-
+       spt     6f-.LPG0(%r13)
+       mvc     __LC_LAST_UPDATE_CLOCK(8),0(%r1)
+       mvc     __LC_LAST_UPDATE_TIMER(8),6f-.LPG0(%r13)
+       mvc     __LC_EXIT_TIMER(8),5f-.LPG0(%r13)
 #ifndef CONFIG_MARCH_G5
        # check processor version against MARCH_{G5,Z900,Z990,Z9_109,Z10}
        stidp   __LC_CPUID              # store cpuid
@@ -500,8 +503,11 @@ startup:basr       %r13,0                  # get base
 
        l       %r13,4f-.LPG0(%r13)
        b       0(%r13)
+       .align  4
 4:     .long   startup_continue
 5:     .long   sched_clock_base_cc
+       .align  8
+6:     .long   0x7fffffff,0xffffffff
 
 #
 # params at 10400 (setup.h)

diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index 163bdfe..7402b6a 100644 (file)
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -434,6 +434,14 @@ setup_lowcore(void)
 #else
        lc->vdso_per_cpu_data = (unsigned long) &lc->paste[0];
 #endif
+       lc->sync_enter_timer = S390_lowcore.sync_enter_timer;
+       lc->async_enter_timer = S390_lowcore.async_enter_timer;
+       lc->exit_timer = S390_lowcore.exit_timer;
+       lc->user_timer = S390_lowcore.user_timer;
+       lc->system_timer = S390_lowcore.system_timer;
+       lc->steal_timer = S390_lowcore.steal_timer;
+       lc->last_update_timer = S390_lowcore.last_update_timer;
+       lc->last_update_clock = S390_lowcore.last_update_clock;
        set_prefix((u32)(unsigned long) lc);
        lowcore_ptr[0] = lc;
 }

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 369ff02..6ded50d 100644 (file)
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -253,32 +253,52 @@ void update_vsyscall_tz(void)
  */
 void __init time_init(void)
 {
+       struct timespec ts;
+       unsigned long flags;
+       cycle_t now;
+
        /* Reset time synchronization interfaces. */
        etr_reset();
        stp_reset();
 
-       /* set xtime */
-       tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, &xtime);
-        set_normalized_timespec(&wall_to_monotonic,
-                                -xtime.tv_sec, -xtime.tv_nsec);
-
        /* request the clock comparator external interrupt */
        if (register_early_external_interrupt(0x1004,
                                              clock_comparator_interrupt,
                                              &ext_int_info_cc) != 0)
                 panic("Couldn't request external interrupt 0x1004");
 
-       if (clocksource_register(&clocksource_tod) != 0)
-               panic("Could not register TOD clock source");
-
        /* request the timing alert external interrupt */
        if (register_early_external_interrupt(0x1406,
                                              timing_alert_interrupt,
                                              &ext_int_etr_cc) != 0)
                panic("Couldn't request external interrupt 0x1406");
 
+       if (clocksource_register(&clocksource_tod) != 0)
+               panic("Could not register TOD clock source");
+
+       /*
+        * The TOD clock is an accurate clock. The xtime should be
+        * initialized in a way that the difference between TOD and
+        * xtime is reasonably small. Too bad that timekeeping_init
+        * sets xtime.tv_nsec to zero. In addition the clock source
+        * change from the jiffies clock source to the TOD clock
+        * source add another error of up to 1/HZ second. The same
+        * function sets wall_to_monotonic to a value that is too
+        * small for /proc/uptime to be accurate.
+        * Reset xtime and wall_to_monotonic to sane values.
+        */
+       write_seqlock_irqsave(&xtime_lock, flags);
+       now = get_clock();
+       tod_to_timeval(now - TOD_UNIX_EPOCH, &xtime);
+       clocksource_tod.cycle_last = now;
+       clocksource_tod.raw_time = xtime;
+       tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, &ts);
+       set_normalized_timespec(&wall_to_monotonic, -ts.tv_sec, -ts.tv_nsec);
+       write_sequnlock_irqrestore(&xtime_lock, flags);
+
        /* Enable TOD clock interrupts on the boot cpu. */
        init_cpu_timer();
+
        /* Enable cpu timer interrupts on the boot cpu. */
        vtime_init();
 }

diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index c0870a6..38ea92f 100644 (file)
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -527,16 +527,8 @@ EXPORT_SYMBOL(del_virt_timer);
  */
 void init_cpu_vtimer(void)
 {
-       struct thread_info *ti = current_thread_info();
        struct vtimer_queue *vq;
 
-       S390_lowcore.user_timer = ti->user_timer;
-       S390_lowcore.system_timer = ti->system_timer;
-
-       /* kick the virtual timer */
-       asm volatile ("STCK %0" : "=m" (S390_lowcore.last_update_clock));
-       asm volatile ("STPT %0" : "=m" (S390_lowcore.last_update_timer));
-
        /* initialize per cpu vtimer structure */
        vq = &__get_cpu_var(virt_cpu_timer);
        INIT_LIST_HEAD(&vq->list);