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/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index 6fa6cf0..55771fd 100644 (file)
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -33,6 +33,19 @@ static void save_stack_address(void *data, unsigned long addr)
                trace->entries[trace->nr_entries++] = addr;
 }
 
+static void save_stack_address_nosched(void *data, unsigned long addr)
+{
+       struct stack_trace *trace = (struct stack_trace *)data;
+       if (in_sched_functions(addr))
+               return;
+       if (trace->skip > 0) {
+               trace->skip--;
+               return;
+       }
+       if (trace->nr_entries < trace->max_entries)
+               trace->entries[trace->nr_entries++] = addr;
+}
+
 static const struct stacktrace_ops save_stack_ops = {
        .warning = save_stack_warning,
        .warning_symbol = save_stack_warning_symbol,
@@ -40,6 +53,13 @@ static const struct stacktrace_ops save_stack_ops = {
        .address = save_stack_address,
 };
 
+static const struct stacktrace_ops save_stack_ops_nosched = {
+       .warning = save_stack_warning,
+       .warning_symbol = save_stack_warning_symbol,
+       .stack = save_stack_stack,
+       .address = save_stack_address_nosched,
+};
+
 /*
  * Save stack-backtrace addresses into a stack_trace buffer.
  */
@@ -50,3 +70,10 @@ void save_stack_trace(struct stack_trace *trace)
                trace->entries[trace->nr_entries++] = ULONG_MAX;
 }
 EXPORT_SYMBOL(save_stack_trace);
+
+void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
+{
+       dump_trace(tsk, NULL, NULL, &save_stack_ops_nosched, trace);
+       if (trace->nr_entries < trace->max_entries)
+               trace->entries[trace->nr_entries++] = ULONG_MAX;
+}

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 7411bfb..91fa8e6 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -310,6 +310,77 @@ static int proc_pid_schedstat(struct task_struct *task, char *buffer)
 }
 #endif
 
+#ifdef CONFIG_LATENCYTOP
+static int lstats_show_proc(struct seq_file *m, void *v)
+{
+       int i;
+       struct task_struct *task = m->private;
+       seq_puts(m, "Latency Top version : v0.1\n");
+
+       for (i = 0; i < 32; i++) {
+               if (task->latency_record[i].backtrace[0]) {
+                       int q;
+                       seq_printf(m, "%i %li %li ",
+                               task->latency_record[i].count,
+                               task->latency_record[i].time,
+                               task->latency_record[i].max);
+                       for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
+                               char sym[KSYM_NAME_LEN];
+                               char *c;
+                               if (!task->latency_record[i].backtrace[q])
+                                       break;
+                               if (task->latency_record[i].backtrace[q] == ULONG_MAX)
+                                       break;
+                               sprint_symbol(sym, task->latency_record[i].backtrace[q]);
+                               c = strchr(sym, '+');
+                               if (c)
+                                       *c = 0;
+                               seq_printf(m, "%s ", sym);
+                       }
+                       seq_printf(m, "\n");
+               }
+
+       }
+       return 0;
+}
+
+static int lstats_open(struct inode *inode, struct file *file)
+{
+       int ret;
+       struct seq_file *m;
+       struct task_struct *task = get_proc_task(inode);
+
+       ret = single_open(file, lstats_show_proc, NULL);
+       if (!ret) {
+               m = file->private_data;
+               m->private = task;
+       }
+       return ret;
+}
+
+static ssize_t lstats_write(struct file *file, const char __user *buf,
+                           size_t count, loff_t *offs)
+{
+       struct seq_file *m;
+       struct task_struct *task;
+
+       m = file->private_data;
+       task = m->private;
+       clear_all_latency_tracing(task);
+
+       return count;
+}
+
+static const struct file_operations proc_lstats_operations = {
+       .open           = lstats_open,
+       .read           = seq_read,
+       .write          = lstats_write,
+       .llseek         = seq_lseek,
+       .release        = single_release,
+};
+
+#endif
+
 /* The badness from the OOM killer */
 unsigned long badness(struct task_struct *p, unsigned long uptime);
 static int proc_oom_score(struct task_struct *task, char *buffer)
@@ -1020,6 +1091,7 @@ static const struct file_operations proc_fault_inject_operations = {
 };
 #endif
 
+
 #ifdef CONFIG_SCHED_DEBUG
 /*
  * Print out various scheduling related per-task fields:
@@ -2230,6 +2302,9 @@ static const struct pid_entry tgid_base_stuff[] = {
 #ifdef CONFIG_SCHEDSTATS
        INF("schedstat",  S_IRUGO, pid_schedstat),
 #endif
+#ifdef CONFIG_LATENCYTOP
+       REG("latency",  S_IRUGO, lstats),
+#endif
 #ifdef CONFIG_PROC_PID_CPUSET
        REG("cpuset",     S_IRUGO, cpuset),
 #endif
@@ -2555,6 +2630,9 @@ static const struct pid_entry tid_base_stuff[] = {
 #ifdef CONFIG_SCHEDSTATS
        INF("schedstat", S_IRUGO, pid_schedstat),
 #endif
+#ifdef CONFIG_LATENCYTOP
+       REG("latency",  S_IRUGO, lstats),
+#endif
 #ifdef CONFIG_PROC_PID_CPUSET
        REG("cpuset",    S_IRUGO, cpuset),
 #endif

diff --git a/include/linux/latencytop.h b/include/linux/latencytop.h
new file mode 100644 (file)
index 0000000..901c2d6
--- /dev/null
+++ b/include/linux/latencytop.h
@@ -0,0 +1,44 @@
+/*
+ * latencytop.h: Infrastructure for displaying latency
+ *
+ * (C) Copyright 2008 Intel Corporation
+ * Author: Arjan van de Ven <arjan@linux.intel.com>
+ *
+ */
+
+#ifndef _INCLUDE_GUARD_LATENCYTOP_H_
+#define _INCLUDE_GUARD_LATENCYTOP_H_
+
+#ifdef CONFIG_LATENCYTOP
+
+#define LT_SAVECOUNT           32
+#define LT_BACKTRACEDEPTH      12
+
+struct latency_record {
+       unsigned long   backtrace[LT_BACKTRACEDEPTH];
+       unsigned int    count;
+       unsigned long   time;
+       unsigned long   max;
+};
+
+
+struct task_struct;
+
+void account_scheduler_latency(struct task_struct *task, int usecs, int inter);
+
+void clear_all_latency_tracing(struct task_struct *p);
+
+#else
+
+static inline void
+account_scheduler_latency(struct task_struct *task, int usecs, int inter)
+{
+}
+
+static inline void clear_all_latency_tracing(struct task_struct *p)
+{
+}
+
+#endif
+
+#endif

diff --git a/include/linux/sched.h b/include/linux/sched.h
index acadcab..dfc76e1 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -88,6 +88,7 @@ struct sched_param {
 #include <linux/hrtimer.h>
 #include <linux/task_io_accounting.h>
 #include <linux/kobject.h>
+#include <linux/latencytop.h>
 
 #include <asm/processor.h>
 
@@ -1220,6 +1221,10 @@ struct task_struct {
        int make_it_fail;
 #endif
        struct prop_local_single dirties;
+#ifdef CONFIG_LATENCYTOP
+       int latency_record_count;
+       struct latency_record latency_record[LT_SAVECOUNT];
+#endif
 };
 
 /*

diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
index e7fa657..5da9794 100644 (file)
--- a/include/linux/stacktrace.h
+++ b/include/linux/stacktrace.h
@@ -9,10 +9,13 @@ struct stack_trace {
 };
 
 extern void save_stack_trace(struct stack_trace *trace);
+extern void save_stack_trace_tsk(struct task_struct *tsk,
+                               struct stack_trace *trace);
 
 extern void print_stack_trace(struct stack_trace *trace, int spaces);
 #else
 # define save_stack_trace(trace)                       do { } while (0)
+# define save_stack_trace_tsk(tsk, trace)              do { } while (0)
 # define print_stack_trace(trace, spaces)              do { } while (0)
 #endif
 

diff --git a/kernel/Makefile b/kernel/Makefile
index 68755cd..390d421 100644 (file)
--- 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 0c969f4..39d22b3 100644 (file)
--- 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 (file)
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);

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 3dab1ff..1b3b40a 100644 (file)
--- 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 3afbd25..5418ef6 100644 (file)
--- 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",

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index a601093..14fb355 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -517,4 +517,18 @@ config FAULT_INJECTION_STACKTRACE_FILTER
        help
          Provide stacktrace filter for fault-injection capabilities
 
+config LATENCYTOP
+       bool "Latency measuring infrastructure"
+       select FRAME_POINTER if !MIPS
+       select KALLSYMS
+       select KALLSYMS_ALL
+       select STACKTRACE
+       select SCHEDSTATS
+       select SCHED_DEBUG
+       depends on X86 || X86_64
+       help
+         Enable this option if you want to use the LatencyTOP tool
+         to find out which userspace is blocking on what kernel operations.
+
+
 source "samples/Kconfig"