[PATCH 2/2] [RESEND] tracing: Add a new workqueue tracer

From: Frederic Weisbecker
Date: Sat Jan 10 2009 - 14:42:24 EST

Sorry I lost two files in the previous 2/2 patch.
Here is the true version
--

The workqueue tracer provides some statistical informations
about each cpu workqueue thread such as the number of the
works inserted and executed since their creation. It can help
to evaluate the amount of work each of them have to perform.
For example it can help a developer to decide whether he should
choose a per cpu workqueue instead of a singlethreaded one.

It only traces statistical informations for now but it will probably later
provide event tracing too.

Such a tracer could help too, and be improved, to help rt priority sorted
workqueue development.

To have a snapshot of the workqueues state at any time, just do

cat /debugfs/tracing/trace_stat/workqueues

Ie:

# CPU INSERTED EXECUTED NAME
# | | | |

1 125 125 reiserfs/1
1 0 0 scsi_tgtd/1
1 0 0 aio/1
1 0 0 ata/1
1 114 114 kblockd/1
1 0 0 kintegrityd/1
1 2144 2147 events/1

0 0 0 kpsmoused
0 105 105 reiserfs/0
0 0 0 scsi_tgtd/0
0 0 0 aio/0
0 0 0 ata_aux
0 0 0 ata/0
0 0 0 cqueue
0 0 0 kacpi_notify
0 0 0 kacpid
0 149 149 kblockd/0
0 0 0 kintegrityd/0
0 1000 1000 khelper
0 2258 2270 events/0

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
---
include/trace/workqueue.h | 25 ++++
kernel/trace/Kconfig | 11 ++
kernel/trace/Makefile | 1 +
kernel/trace/trace_workqueue.c | 273 ++++++++++++++++++++++++++++++++++++++++
kernel/workqueue.c | 16 +++-
5 files changed, 325 insertions(+), 1 deletions(-)

diff --git a/include/trace/workqueue.h b/include/trace/workqueue.h
new file mode 100644
index 0000000..867829d
--- /dev/null
+++ b/include/trace/workqueue.h
@@ -0,0 +1,25 @@
+#ifndef __TRACE_WORKQUEUE_H
+#define __TRACE_WORKQUEUE_H
+
+#include <linux/tracepoint.h>
+#include <linux/workqueue.h>
+#include <linux/sched.h>
+
+DECLARE_TRACE(workqueue_insertion,
+ TPPROTO(struct task_struct *wq_thread, struct work_struct *work),
+ TPARGS(wq_thread, work));
+
+DECLARE_TRACE(workqueue_execution,
+ TPPROTO(struct task_struct *wq_thread, struct work_struct *work),
+ TPARGS(wq_thread, work));
+
+/* Trace the creation of one workqueue thread on a cpu */
+DECLARE_TRACE(workqueue_creation,
+ TPPROTO(struct task_struct *wq_thread, int cpu),
+ TPARGS(wq_thread, cpu));
+
+DECLARE_TRACE(workqueue_destruction,
+ TPPROTO(struct task_struct *wq_thread),
+ TPARGS(wq_thread));
+
+#endif /* __TRACE_WORKQUEUE_H */
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 1c0b750..9ba1c68 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -284,6 +284,17 @@ config KMEMTRACE

If unsure, say N.

+config WORKQUEUE_TRACER
+ bool "Trace workqueues"
+ select TRACING
+ help
+ The workqueue tracer provides some statistical informations
+ about each cpu workqueue thread such as the number of the
+ works inserted and executed since their creation. It can help
+ to evaluate the amount of work each of them have to perform.
+ For example it can help a developer to decide whether he should
+ choose a per cpu workqueue instead of a singlethreaded one.
+

config DYNAMIC_FTRACE
bool "enable/disable ftrace tracepoints dynamically"
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index 05c9182..f76d48f 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -36,5 +36,6 @@ obj-$(CONFIG_TRACE_BRANCH_PROFILING) += trace_branch.o
obj-$(CONFIG_HW_BRANCH_TRACER) += trace_hw_branches.o
obj-$(CONFIG_POWER_TRACER) += trace_power.o
obj-$(CONFIG_KMEMTRACE) += kmemtrace.o
+obj-$(CONFIG_WORKQUEUE_TRACER) += trace_workqueue.o

libftrace-y := ftrace.o
diff --git a/kernel/trace/trace_workqueue.c b/kernel/trace/trace_workqueue.c
new file mode 100644
index 0000000..f006135
--- /dev/null
+++ b/kernel/trace/trace_workqueue.c
@@ -0,0 +1,273 @@
+/*
+ * Workqueue statistical tracer.
+ *
+ * Copyright (C) 2008 Frederic Weisbecker <fweisbec@xxxxxxxxx>
+ *
+ */
+
+
+#include <trace/workqueue.h>
+#include <linux/list.h>
+#include "trace_stat.h"
+#include "trace.h"
+
+
+/* A list of cpu workqueue threads on one Cpu */
+struct cpu_workqueue_stats {
+ struct list_head list;
+/* Useful to know if we print the cpu headers */
+ bool first_entry;
+ int cpu;
+ pid_t pid;
+/* Can be inserted from interrupt or user context, need to be atomic */
+ atomic_t inserted;
+/*
+ * Don't need to be atomic, works are serialized in a single workqueue thread
+ * on a single CPU.
+ */
+ unsigned int executed;
+};
+
+
+
+static spinlock_t cpu_wq_list_lock[NR_CPUS];
+
+/* List of cpu workqueue thread, listed by cpu */
+static struct list_head cpu_wq_list[NR_CPUS];
+
+/* Insertion of a work */
+static void
+probe_workqueue_insertion(struct task_struct *wq_thread,
+ struct work_struct *work)
+{
+ int cpu = cpumask_first(&wq_thread->cpus_allowed);
+ struct cpu_workqueue_stats *node, *next;
+ unsigned long flags;
+
+ spin_lock_irqsave(&cpu_wq_list_lock[cpu], flags);
+ list_for_each_entry_safe(node, next, &cpu_wq_list[cpu], list) {
+ if (node->pid == wq_thread->pid) {
+ atomic_inc(&node->inserted);
+ goto found;
+ }
+ }
+ pr_debug("trace_workqueue: entry not found\n");
+found:
+ spin_unlock_irqrestore(&cpu_wq_list_lock[cpu], flags);
+}
+
+/* Execution of a work */
+static void
+probe_workqueue_execution(struct task_struct *wq_thread,
+ struct work_struct *work)
+{
+ int cpu = cpumask_first(&wq_thread->cpus_allowed);
+ struct cpu_workqueue_stats *node, *next;
+ unsigned long flags;
+
+ spin_lock_irqsave(&cpu_wq_list_lock[cpu], flags);
+ list_for_each_entry_safe(node, next, &cpu_wq_list[cpu], list) {
+ if (node->pid == wq_thread->pid) {
+ node->executed++;
+ goto found;
+ }
+ }
+ pr_debug("trace_workqueue: entry not found\n");
+found:
+ spin_unlock_irqrestore(&cpu_wq_list_lock[cpu], flags);
+}
+
+/* Creation of a cpu workqueue thread */
+static void probe_workqueue_creation(struct task_struct *wq_thread, int cpu)
+{
+ struct cpu_workqueue_stats *cws;
+ unsigned long flags;
+
+ WARN_ON(cpu < 0 || cpu >= NR_CPUS);
+
+ /* Workqueues are sometimes created in atomic context */
+ cws = kzalloc(sizeof(struct cpu_workqueue_stats), GFP_ATOMIC);
+ if (!cws) {
+ pr_warning("trace_workqueue: not enough memory\n");
+ return;
+ }
+ tracing_record_cmdline(wq_thread);
+
+ INIT_LIST_HEAD(&cws->list);
+ cws->cpu = cpu;
+
+ cws->pid = wq_thread->pid;
+
+ spin_lock_irqsave(&cpu_wq_list_lock[cpu], flags);
+ if (list_empty(&cpu_wq_list[cpu]))
+ cws->first_entry = true;
+ list_add_tail(&cws->list, &cpu_wq_list[cpu]);
+ spin_unlock_irqrestore(&cpu_wq_list_lock[cpu], flags);
+}
+
+/* Destruction of a cpu workqueue thread */
+static void probe_workqueue_destruction(struct task_struct *wq_thread)
+{
+ /* Workqueue only execute on one cpu */
+ int cpu = cpumask_first(&wq_thread->cpus_allowed);
+ struct cpu_workqueue_stats *node, *next;
+ unsigned long flags;
+
+ spin_lock_irqsave(&cpu_wq_list_lock[cpu], flags);
+ list_for_each_entry_safe(node, next, &cpu_wq_list[cpu], list) {
+ if (node->pid == wq_thread->pid) {
+ list_del(&node->list);
+ kfree(node);
+ goto found;
+ }
+ }
+
+ pr_debug("trace_workqueue: don't find workqueue to destroy\n");
+found:
+ spin_unlock_irqrestore(&cpu_wq_list_lock[cpu], flags);
+
+}
+
+static struct cpu_workqueue_stats *workqueue_stat_start_cpu(int cpu)
+{
+ unsigned long flags;
+ struct cpu_workqueue_stats *ret = NULL;
+
+
+ spin_lock_irqsave(&cpu_wq_list_lock[cpu], flags);
+
+ if (!list_empty(&cpu_wq_list[cpu]))
+ ret = list_entry(cpu_wq_list[cpu].next,
+ struct cpu_workqueue_stats, list);
+
+ spin_unlock_irqrestore(&cpu_wq_list_lock[cpu], flags);
+
+ return ret;
+}
+
+static void *workqueue_stat_start(void)
+{
+ int i;
+ void *ret = NULL;
+
+ for (i = 0; i < NR_CPUS; i++) {
+
+ ret = workqueue_stat_start_cpu(i);
+ if (ret)
+ return ret;
+ }
+ return NULL;
+}
+
+static void *workqueue_stat_next(void *prev, int idx)
+{
+ struct cpu_workqueue_stats *prev_cws = prev;
+ int cpu = prev_cws->cpu;
+ unsigned long flags;
+ void *ret = NULL;
+
+ spin_lock_irqsave(&cpu_wq_list_lock[cpu], flags);
+ if (list_is_last(&prev_cws->list, &cpu_wq_list[cpu])) {
+ spin_unlock_irqrestore(&cpu_wq_list_lock[cpu], flags);
+ for (++cpu ; cpu < NR_CPUS; cpu++) {
+ ret = workqueue_stat_start_cpu(cpu);
+ if (ret)
+ return ret;
+ }
+ return NULL;
+ }
+ spin_unlock_irqrestore(&cpu_wq_list_lock[cpu], flags);
+
+ return list_entry(prev_cws->list.next, struct cpu_workqueue_stats,
+ list);
+}
+
+static int workqueue_stat_show(struct seq_file *s, void *p)
+{
+ struct cpu_workqueue_stats *cws = p;
+ unsigned long flags;
+ int cpu = cws->cpu;
+
+ seq_printf(s, "%3d %6d %6u %s\n", cws->cpu,
+ atomic_read(&cws->inserted),
+ cws->executed,
+ trace_find_cmdline(cws->pid));
+
+ spin_lock_irqsave(&cpu_wq_list_lock[cpu], flags);
+ if (&cws->list == cpu_wq_list[cpu].next)
+ seq_printf(s, "\n");
+ spin_unlock_irqrestore(&cpu_wq_list_lock[cpu], flags);
+
+ return 0;
+}
+
+static int workqueue_stat_headers(struct seq_file *s)
+{
+ seq_printf(s, "# CPU INSERTED EXECUTED NAME\n");
+ seq_printf(s, "# | | | |\n\n");
+ return 0;
+}
+
+struct tracer_stat workqueue_stats __read_mostly = {
+ .name = "workqueues",
+ .stat_start = workqueue_stat_start,
+ .stat_next = workqueue_stat_next,
+ .stat_show = workqueue_stat_show,
+ .stat_headers = workqueue_stat_headers
+};
+
+
+int __init stat_workqueue_init(void)
+{
+ if (register_stat_tracer(&workqueue_stats)) {
+ pr_warning("Unable to register workqueue stat tracer\n");
+ return 1;
+ }
+
+ return 0;
+}
+fs_initcall(stat_workqueue_init);
+
+/*
+ * Workqueues are created very early, just after pre-smp initcalls.
+ * So we must register our tracepoints at this stage.
+ */
+int __init trace_workqueue_early_init(void)
+{
+ int ret, i;
+
+ ret = register_trace_workqueue_insertion(probe_workqueue_insertion);
+ if (ret)
+ goto out;
+
+ ret = register_trace_workqueue_execution(probe_workqueue_execution);
+ if (ret)
+ goto no_insertion;
+
+ ret = register_trace_workqueue_creation(probe_workqueue_creation);
+ if (ret)
+ goto no_execution;
+
+ ret = register_trace_workqueue_destruction(probe_workqueue_destruction);
+ if (ret)
+ goto no_creation;
+
+ for (i = 0; i < NR_CPUS; i++) {
+ spin_lock_init(&cpu_wq_list_lock[i]);
+ INIT_LIST_HEAD(&cpu_wq_list[i]);
+ }
+
+ return 0;
+
+no_creation:
+ unregister_trace_workqueue_creation(probe_workqueue_creation);
+no_execution:
+ unregister_trace_workqueue_execution(probe_workqueue_execution);
+no_insertion:
+ unregister_trace_workqueue_insertion(probe_workqueue_insertion);
+out:
+ pr_warning("trace_workqueue: unable to trace workqueues\n");
+
+ return 1;
+}
+early_initcall(trace_workqueue_early_init);
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 2f44583..71145f8 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -33,6 +33,7 @@
#include <linux/kallsyms.h>
#include <linux/debug_locks.h>
#include <linux/lockdep.h>
+#include <trace/workqueue.h>

/*
* The per-CPU workqueue (if single thread, we always use the first
@@ -138,11 +139,15 @@ static void insert_work(struct cpu_workqueue_struct *cwq,
wake_up(&cwq->more_work);
}

+DEFINE_TRACE(workqueue_insertion);
+
static void __queue_work(struct cpu_workqueue_struct *cwq,
struct work_struct *work)
{
unsigned long flags;

+ trace_workqueue_insertion(cwq->thread, work);
+
spin_lock_irqsave(&cwq->lock, flags);
insert_work(cwq, work, &cwq->worklist);
spin_unlock_irqrestore(&cwq->lock, flags);
@@ -259,6 +264,8 @@ int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
}
EXPORT_SYMBOL_GPL(queue_delayed_work_on);

+DEFINE_TRACE(workqueue_execution);
+
static void run_workqueue(struct cpu_workqueue_struct *cwq)
{
spin_lock_irq(&cwq->lock);
@@ -284,7 +291,7 @@ static void run_workqueue(struct cpu_workqueue_struct *cwq)
*/
struct lockdep_map lockdep_map = work->lockdep_map;
#endif
-
+ trace_workqueue_execution(cwq->thread, work);
cwq->current_work = work;
list_del_init(cwq->worklist.next);
spin_unlock_irq(&cwq->lock);
@@ -765,6 +772,8 @@ init_cpu_workqueue(struct workqueue_struct *wq, int cpu)
return cwq;
}

+DEFINE_TRACE(workqueue_creation);
+
static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
{
struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
@@ -787,6 +796,8 @@ static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
cwq->thread = p;

+ trace_workqueue_creation(cwq->thread, cpu);
+
return 0;
}

@@ -868,6 +879,8 @@ struct workqueue_struct *__create_workqueue_key(const char *name,
}
EXPORT_SYMBOL_GPL(__create_workqueue_key);

+DEFINE_TRACE(workqueue_destruction);
+
static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq)
{
/*
@@ -891,6 +904,7 @@ static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq)
* checks list_empty(), and a "normal" queue_work() can't use
* a dead CPU.
*/
+ trace_workqueue_destruction(cwq->thread);
kthread_stop(cwq->thread);
cwq->thread = NULL;
}
--
1.6.0.4


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/