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>

1 files changed, 239 insertions, 0 deletions

diff --git a/kernel/latencytop.c b/kernel/latencytop.c
new file mode 100644
index 000000000000..b4e3c85abe74
--- /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);