diff options
author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2008-12-31 15:11:40 +0100 |
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committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2008-12-31 15:11:47 +0100 |
commit | 6f43092441bda528dd38f2dc6c1e2522c5079fb7 (patch) | |
tree | e8bba1cf80b19be3e3658b9351b32469ba8c6bac /arch/s390/kernel/process.c | |
parent | aa5e97ce4bbc9d5daeec16b1d15bb3f6b7b4f4d4 (diff) | |
download | linux-rt-6f43092441bda528dd38f2dc6c1e2522c5079fb7.tar.gz |
[PATCH] improve precision of idle time detection.
Increase the precision of the idle time calculation that is exported
to user space via /sys/devices/system/cpu/cpu<x>/idle_time_us
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel/process.c')
-rw-r--r-- | arch/s390/kernel/process.c | 67 |
1 files changed, 45 insertions, 22 deletions
diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c index 04f8c67a6101..1e06436f07c2 100644 --- a/arch/s390/kernel/process.c +++ b/arch/s390/kernel/process.c @@ -38,6 +38,7 @@ #include <linux/utsname.h> #include <linux/tick.h> #include <linux/elfcore.h> +#include <linux/kernel_stat.h> #include <asm/uaccess.h> #include <asm/pgtable.h> #include <asm/system.h> @@ -79,30 +80,19 @@ DEFINE_PER_CPU(struct s390_idle_data, s390_idle) = { .lock = __SPIN_LOCK_UNLOCKED(s390_idle.lock) }; -static int s390_idle_enter(void) +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++; - idle->in_idle = 1; - idle->idle_enter = get_clock(); spin_unlock(&idle->lock); - vtime_stop_cpu_timer(); - return NOTIFY_OK; -} - -void s390_idle_leave(void) -{ - struct s390_idle_data *idle; - vtime_start_cpu_timer(); - idle = &__get_cpu_var(s390_idle); - spin_lock(&idle->lock); - idle->idle_time += get_clock() - idle->idle_enter; - idle->in_idle = 0; - spin_unlock(&idle->lock); } extern void s390_handle_mcck(void); @@ -111,16 +101,16 @@ extern void s390_handle_mcck(void); */ 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()) { local_irq_enable(); return; } - if (s390_idle_enter() == NOTIFY_BAD) { - local_irq_enable(); - return; - } #ifdef CONFIG_HOTPLUG_CPU if (cpu_is_offline(smp_processor_id())) { preempt_enable_no_resched(); @@ -138,9 +128,42 @@ 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. */ - __load_psw_mask(psw_kernel_bits | PSW_MASK_WAIT | - PSW_MASK_IO | PSW_MASK_EXT); + 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__ */ start_critical_timings(); } |