sched: latencytop support
LatencyTOP kernel infrastructure; it measures latencies in the
scheduler and tracks it system wide and per process.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/latencytop.c b/kernel/latencytop.c
new file mode 100644
index 0000000..b4e3c85
--- /dev/null
+++ b/kernel/latencytop.c
@@ -0,0 +1,239 @@
+/*
+ * latencytop.c: Latency display infrastructure
+ *
+ * (C) Copyright 2008 Intel Corporation
+ * Author: Arjan van de Ven <arjan@linux.intel.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License.
+ */
+#include <linux/latencytop.h>
+#include <linux/kallsyms.h>
+#include <linux/seq_file.h>
+#include <linux/notifier.h>
+#include <linux/spinlock.h>
+#include <linux/proc_fs.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/stacktrace.h>
+
+static DEFINE_SPINLOCK(latency_lock);
+
+#define MAXLR 128
+static struct latency_record latency_record[MAXLR];
+
+int latencytop_enabled;
+
+void clear_all_latency_tracing(struct task_struct *p)
+{
+ unsigned long flags;
+
+ if (!latencytop_enabled)
+ return;
+
+ spin_lock_irqsave(&latency_lock, flags);
+ memset(&p->latency_record, 0, sizeof(p->latency_record));
+ p->latency_record_count = 0;
+ spin_unlock_irqrestore(&latency_lock, flags);
+}
+
+static void clear_global_latency_tracing(void)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&latency_lock, flags);
+ memset(&latency_record, 0, sizeof(latency_record));
+ spin_unlock_irqrestore(&latency_lock, flags);
+}
+
+static void __sched
+account_global_scheduler_latency(struct task_struct *tsk, struct latency_record *lat)
+{
+ int firstnonnull = MAXLR + 1;
+ int i;
+
+ if (!latencytop_enabled)
+ return;
+
+ /* skip kernel threads for now */
+ if (!tsk->mm)
+ return;
+
+ for (i = 0; i < MAXLR; i++) {
+ int q;
+ int same = 1;
+ /* Nothing stored: */
+ if (!latency_record[i].backtrace[0]) {
+ if (firstnonnull > i)
+ firstnonnull = i;
+ continue;
+ }
+ for (q = 0 ; q < LT_BACKTRACEDEPTH ; q++) {
+ if (latency_record[i].backtrace[q] !=
+ lat->backtrace[q])
+ same = 0;
+ if (same && lat->backtrace[q] == 0)
+ break;
+ if (same && lat->backtrace[q] == ULONG_MAX)
+ break;
+ }
+ if (same) {
+ latency_record[i].count++;
+ latency_record[i].time += lat->time;
+ if (lat->time > latency_record[i].max)
+ latency_record[i].max = lat->time;
+ return;
+ }
+ }
+
+ i = firstnonnull;
+ if (i >= MAXLR - 1)
+ return;
+
+ /* Allocted a new one: */
+ memcpy(&latency_record[i], lat, sizeof(struct latency_record));
+}
+
+static inline void store_stacktrace(struct task_struct *tsk, struct latency_record *lat)
+{
+ struct stack_trace trace;
+
+ memset(&trace, 0, sizeof(trace));
+ trace.max_entries = LT_BACKTRACEDEPTH;
+ trace.entries = &lat->backtrace[0];
+ trace.skip = 0;
+ save_stack_trace_tsk(tsk, &trace);
+}
+
+void __sched
+account_scheduler_latency(struct task_struct *tsk, int usecs, int inter)
+{
+ unsigned long flags;
+ int i, q;
+ struct latency_record lat;
+
+ if (!latencytop_enabled)
+ return;
+
+ /* Long interruptible waits are generally user requested... */
+ if (inter && usecs > 5000)
+ return;
+
+ memset(&lat, 0, sizeof(lat));
+ lat.count = 1;
+ lat.time = usecs;
+ lat.max = usecs;
+ store_stacktrace(tsk, &lat);
+
+ spin_lock_irqsave(&latency_lock, flags);
+
+ account_global_scheduler_latency(tsk, &lat);
+
+ /*
+ * short term hack; if we're > 32 we stop; future we recycle:
+ */
+ tsk->latency_record_count++;
+ if (tsk->latency_record_count >= LT_SAVECOUNT)
+ goto out_unlock;
+
+ for (i = 0; i < LT_SAVECOUNT ; i++) {
+ struct latency_record *mylat;
+ int same = 1;
+ mylat = &tsk->latency_record[i];
+ for (q = 0 ; q < LT_BACKTRACEDEPTH ; q++) {
+ if (mylat->backtrace[q] !=
+ lat.backtrace[q])
+ same = 0;
+ if (same && lat.backtrace[q] == 0)
+ break;
+ if (same && lat.backtrace[q] == ULONG_MAX)
+ break;
+ }
+ if (same) {
+ mylat->count++;
+ mylat->time += lat.time;
+ if (lat.time > mylat->max)
+ mylat->max = lat.time;
+ goto out_unlock;
+ }
+ }
+
+ /* Allocated a new one: */
+ i = tsk->latency_record_count;
+ memcpy(&tsk->latency_record[i], &lat, sizeof(struct latency_record));
+
+out_unlock:
+ spin_unlock_irqrestore(&latency_lock, flags);
+}
+
+static int lstats_show(struct seq_file *m, void *v)
+{
+ int i;
+
+ seq_puts(m, "Latency Top version : v0.1\n");
+
+ for (i = 0; i < MAXLR; i++) {
+ if (latency_record[i].backtrace[0]) {
+ int q;
+ seq_printf(m, "%i %li %li ",
+ latency_record[i].count,
+ latency_record[i].time,
+ latency_record[i].max);
+ for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
+ char sym[KSYM_NAME_LEN];
+ char *c;
+ if (!latency_record[i].backtrace[q])
+ break;
+ if (latency_record[i].backtrace[q] == ULONG_MAX)
+ break;
+ sprint_symbol(sym, latency_record[i].backtrace[q]);
+ c = strchr(sym, '+');
+ if (c)
+ *c = 0;
+ seq_printf(m, "%s ", sym);
+ }
+ seq_printf(m, "\n");
+ }
+ }
+ return 0;
+}
+
+static ssize_t
+lstats_write(struct file *file, const char __user *buf, size_t count,
+ loff_t *offs)
+{
+ clear_global_latency_tracing();
+
+ return count;
+}
+
+static int lstats_open(struct inode *inode, struct file *filp)
+{
+ return single_open(filp, lstats_show, NULL);
+}
+
+static struct file_operations lstats_fops = {
+ .open = lstats_open,
+ .read = seq_read,
+ .write = lstats_write,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+static int __init init_lstats_procfs(void)
+{
+ struct proc_dir_entry *pe;
+
+ pe = create_proc_entry("latency_stats", 0644, NULL);
+ if (!pe)
+ return -ENOMEM;
+
+ pe->proc_fops = &lstats_fops;
+
+ return 0;
+}
+__initcall(init_lstats_procfs);