procfs: speed up /proc/pid/stat, statm

[cascardo/linux.git] / kernel / watchdog.c

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index d117262..df30ee0 100644 (file)
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -3,15 +3,14 @@
  *
  * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
  *
- * this code detects hard lockups: incidents in where on a CPU
- * the kernel does not respond to anything except NMI.
- *
- * Note: Most of this code is borrowed heavily from softlockup.c,
- * so thanks to Ingo for the initial implementation.
- * Some chunks also taken from arch/x86/kernel/apic/nmi.c, thanks
+ * Note: Most of this code is borrowed heavily from the original softlockup
+ * detector, so thanks to Ingo for the initial implementation.
+ * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
  * to those contributors as well.
  */
 
+#define pr_fmt(fmt) "NMI watchdog: " fmt
+
 #include <linux/mm.h>
 #include <linux/cpu.h>
 #include <linux/nmi.h>
@@ -117,9 +116,10 @@ static unsigned long get_sample_period(void)
 {
        /*
         * convert watchdog_thresh from seconds to ns
-        * the divide by 5 is to give hrtimer 5 chances to
-        * increment before the hardlockup detector generates
-        * a warning
+        * the divide by 5 is to give hrtimer several chances (two
+        * or three with the current relation between the soft
+        * and hard thresholds) to increment before the
+        * hardlockup detector generates a warning
         */
        return get_softlockup_thresh() * (NSEC_PER_SEC / 5);
 }
@@ -321,11 +321,9 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
  */
 static int watchdog(void *unused)
 {
-       struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
+       struct sched_param param = { .sched_priority = 0 };
        struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
 
-       sched_setscheduler(current, SCHED_FIFO, &param);
-
        /* initialize timestamp */
        __touch_watchdog();
 
@@ -336,9 +334,11 @@ static int watchdog(void *unused)
 
        set_current_state(TASK_INTERRUPTIBLE);
        /*
-        * Run briefly once per second to reset the softlockup timestamp.
-        * If this gets delayed for more than 60 seconds then the
-        * debug-printout triggers in watchdog_timer_fn().
+        * Run briefly (kicked by the hrtimer callback function) once every
+        * get_sample_period() seconds (4 seconds by default) to reset the
+        * softlockup timestamp. If this gets delayed for more than
+        * 2*watchdog_thresh seconds then the debug-printout triggers in
+        * watchdog_timer_fn().
         */
        while (!kthread_should_stop()) {
                __touch_watchdog();
@@ -349,8 +349,11 @@ static int watchdog(void *unused)
 
                set_current_state(TASK_INTERRUPTIBLE);
        }
+       /*
+        * Drop the policy/priority elevation during thread exit to avoid a
+        * scheduling latency spike.
+        */
        __set_current_state(TASK_RUNNING);
-       param.sched_priority = 0;
        sched_setscheduler(current, SCHED_NORMAL, &param);
        return 0;
 }
@@ -376,18 +379,20 @@ static int watchdog_nmi_enable(int cpu)
        /* Try to register using hardware perf events */
        event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
        if (!IS_ERR(event)) {
-               printk(KERN_INFO "NMI watchdog enabled, takes one hw-pmu counter.\n");
+               pr_info("enabled, takes one hw-pmu counter.\n");
                goto out_save;
        }
 
 
        /* vary the KERN level based on the returned errno */
        if (PTR_ERR(event) == -EOPNOTSUPP)
-               printk(KERN_INFO "NMI watchdog disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
+               pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
        else if (PTR_ERR(event) == -ENOENT)
-               printk(KERN_WARNING "NMI watchdog disabled (cpu%i): hardware events not enabled\n", cpu);
+               pr_warning("disabled (cpu%i): hardware events not enabled\n",
+                        cpu);
        else
-               printk(KERN_ERR "NMI watchdog disabled (cpu%i): unable to create perf event: %ld\n", cpu, PTR_ERR(event));
+               pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
+                       cpu, PTR_ERR(event));
        return PTR_ERR(event);
 
        /* success path */
@@ -439,9 +444,10 @@ static int watchdog_enable(int cpu)
 
        /* create the watchdog thread */
        if (!p) {
+               struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
                p = kthread_create_on_node(watchdog, NULL, cpu_to_node(cpu), "watchdog/%d", cpu);
                if (IS_ERR(p)) {
-                       printk(KERN_ERR "softlockup watchdog for %i failed\n", cpu);
+                       pr_err("softlockup watchdog for %i failed\n", cpu);
                        if (!err) {
                                /* if hardlockup hasn't already set this */
                                err = PTR_ERR(p);
@@ -450,6 +456,7 @@ static int watchdog_enable(int cpu)
                        }
                        goto out;
                }
+               sched_setscheduler(p, SCHED_FIFO, &param);
                kthread_bind(p, cpu);
                per_cpu(watchdog_touch_ts, cpu) = 0;
                per_cpu(softlockup_watchdog, cpu) = p;
@@ -496,7 +503,7 @@ static void watchdog_enable_all_cpus(void)
                        watchdog_enabled = 1;
 
        if (!watchdog_enabled)
-               printk(KERN_ERR "watchdog: failed to be enabled on some cpus\n");
+               pr_err("failed to be enabled on some cpus\n");
 
 }