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>

5 files changed, 258 insertions, 1 deletions

diff --git a/kernel/Makefile b/kernel/Makefile
index 68755cd9a7e4..390d42146267 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -62,6 +62,7 @@ obj-$(CONFIG_SYSCTL) += utsname_sysctl.o
 obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o
 obj-$(CONFIG_TASKSTATS) += taskstats.o tsacct.o
 obj-$(CONFIG_MARKERS) += marker.o
+obj-$(CONFIG_LATENCYTOP) += latencytop.o
 
 ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
 # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
diff --git a/kernel/fork.c b/kernel/fork.c
index 0c969f4fade0..39d22b3357de 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1205,6 +1205,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 #ifdef TIF_SYSCALL_EMU
         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
 #endif
+        clear_all_latency_tracing(p);
 
         /* Our parent execution domain becomes current domain
            These must match for thread signalling to apply */
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);
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 3dab1ff83c4f..1b3b40ad7c54 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -20,6 +20,8 @@
  *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
  */
 
+#include <linux/latencytop.h>
+
 /*
  * Targeted preemption latency for CPU-bound tasks:
  * (default: 20ms * (1 + ilog(ncpus)), units: nanoseconds)
@@ -434,6 +436,7 @@ static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
 #ifdef CONFIG_SCHEDSTATS
         if (se->sleep_start) {
                 u64 delta = rq_of(cfs_rq)->clock - se->sleep_start;
+                struct task_struct *tsk = task_of(se);
 
                 if ((s64)delta < 0)
                         delta = 0;
@@ -443,9 +446,12 @@ static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
 
                 se->sleep_start = 0;
                 se->sum_sleep_runtime += delta;
+
+                account_scheduler_latency(tsk, delta >> 10, 1);
         }
         if (se->block_start) {
                 u64 delta = rq_of(cfs_rq)->clock - se->block_start;
+                struct task_struct *tsk = task_of(se);
 
                 if ((s64)delta < 0)
                         delta = 0;
@@ -462,11 +468,11 @@ static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
                  * time that the task spent sleeping:
                  */
                 if (unlikely(prof_on == SLEEP_PROFILING)) {
-                        struct task_struct *tsk = task_of(se);
 
                         profile_hits(SLEEP_PROFILING, (void *)get_wchan(tsk),
                                      delta >> 20);
                 }
+                account_scheduler_latency(tsk, delta >> 10, 0);
         }
 #endif
 }
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 3afbd25f43eb..5418ef61e16e 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -81,6 +81,7 @@ extern int compat_log;
 extern int maps_protect;
 extern int sysctl_stat_interval;
 extern int audit_argv_kb;
+extern int latencytop_enabled;
 
 /* Constants used for minimum and  maximum */
 #ifdef CONFIG_DETECT_SOFTLOCKUP
@@ -416,6 +417,15 @@ static struct ctl_table kern_table[] = {
                 .proc_handler   = &proc_dointvec_taint,
         },
 #endif
+#ifdef CONFIG_LATENCYTOP
+        {
+                .procname       = "latencytop",
+                .data           = &latencytop_enabled,
+                .maxlen         = sizeof(int),
+                .mode           = 0644,
+                .proc_handler   = &proc_dointvec,
+        },
+#endif
 #ifdef CONFIG_SECURITY_CAPABILITIES
         {
                 .procname       = "cap-bound",