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



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

> +
> + 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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