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SubjectRe: [PATCH 2/2] [RESEND] tracing: Add a new workqueue tracer
On Mon, Jan 12, 2009 at 01:15:49PM -0500, Steven Rostedt wrote:
>
>
>
> On Sat, 10 Jan 2009, Frederic Weisbecker wrote:
>
> > 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@gmail.com>
> > ---
> > 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@gmail.com>
> > + *
> > + */
> > +
> > +
> > +#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++) {
>
> Hi Frederic,
>
> I'm getting these warnings from checkpatch.pl, and I think they are
> correct:
>
> WARNING: usage of NR_CPUS is often wrong - consider using cpu_possible(),
> num_possible_cpus(), for_each_possible_cpu(), etc
> #953: FILE: kernel/trace/trace_workqueue.c:153:
> + for (i = 0; i < NR_CPUS; i++) {
>
> We should probably change them to for_each_possible_cpu, or online cpu.
>
> -- Steve


I found it very convenient because I didn't have to allocate
my cpu list array dynamically with it :-)

I'm preparing a v2...


> > +
> > + 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
> >
> >
> >
> >



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