Re: [PATCH -tip] trace_workqueue: use percpu data for workqueue stat

Frédéric Weisbecker
2009-01-15T13:10:20Z

Hi Lai,

2009/1/15 Lai Jiangshan <laijs@cn.fujitsu.com>:
>
> Impact: make trace_workqueue works well on NUMA
>
> It's not correct when (num_possible_cpus() < nr_cpumask_bits):
> all_workqueue_stat = kmalloc(sizeof(struct workqueue_global_stats)
> * num_possible_cpus(), GFP_KERNEL);

What is the difference between num_possible_cpus() and nr_cpumask_bits actually?
It looks like nr_cpumask_bits binds to NR_CPUS on early time and after
it is set to
num_possible_cpus() , right?
In this case num_possible_cpus() seems more relevant...no?

(I'm pretty sure I'm wrong.... :-)

> And alloc_percpu() allocate the cpu's data on the cpu's memory node.

Ok.

Thanks.
Frederic.

> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> ---
> diff --git a/kernel/trace/trace_workqueue.c b/kernel/trace/trace_workqueue.c
> index f8118d3..79617e2 100644
> --- a/kernel/trace/trace_workqueue.c
> +++ b/kernel/trace/trace_workqueue.c
> @@ -8,6 +8,7 @@
>
> #include <trace/workqueue.h>
> #include <linux/list.h>
> +#include <linux/percpu.h>
> #include "trace_stat.h"
> #include "trace.h"
>
> @@ -38,6 +39,7 @@ struct workqueue_global_stats {
> * never freed.
> */
> static struct workqueue_global_stats *all_workqueue_stat;
> +#define workqueue_cpu_stat(cpu) per_cpu_ptr(all_workqueue_stat, cpu)
>
> /* Insertion of a work */
> static void
> @@ -48,8 +50,8 @@ probe_workqueue_insertion(struct task_struct *wq_thread,
> struct cpu_workqueue_stats *node, *next;
> unsigned long flags;
>
> - spin_lock_irqsave(&all_workqueue_stat[cpu].lock, flags);
> - list_for_each_entry_safe(node, next, &all_workqueue_stat[cpu].list,
> + spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
> + list_for_each_entry_safe(node, next, &workqueue_cpu_stat(cpu)->list,
> list) {
> if (node->pid == wq_thread->pid) {
> atomic_inc(&node->inserted);
> @@ -58,7 +60,7 @@ probe_workqueue_insertion(struct task_struct *wq_thread,
> }
> pr_debug("trace_workqueue: entry not found\n");
> found:
> - spin_unlock_irqrestore(&all_workqueue_stat[cpu].lock, flags);
> + spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
> }
>
> /* Execution of a work */
> @@ -70,8 +72,8 @@ probe_workqueue_execution(struct task_struct *wq_thread,
> struct cpu_workqueue_stats *node, *next;
> unsigned long flags;
>
> - spin_lock_irqsave(&all_workqueue_stat[cpu].lock, flags);
> - list_for_each_entry_safe(node, next, &all_workqueue_stat[cpu].list,
> + spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
> + list_for_each_entry_safe(node, next, &workqueue_cpu_stat(cpu)->list,
> list) {
> if (node->pid == wq_thread->pid) {
> node->executed++;
> @@ -80,7 +82,7 @@ probe_workqueue_execution(struct task_struct *wq_thread,
> }
> pr_debug("trace_workqueue: entry not found\n");
> found:
> - spin_unlock_irqrestore(&all_workqueue_stat[cpu].lock, flags);
> + spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
> }
>
> /* Creation of a cpu workqueue thread */
> @@ -104,11 +106,11 @@ static void probe_workqueue_creation(struct task_struct *wq_thread, int cpu)
>
> cws->pid = wq_thread->pid;
>
> - spin_lock_irqsave(&all_workqueue_stat[cpu].lock, flags);
> - if (list_empty(&all_workqueue_stat[cpu].list))
> + spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
> + if (list_empty(&workqueue_cpu_stat(cpu)->list))
> cws->first_entry = true;
> - list_add_tail(&cws->list, &all_workqueue_stat[cpu].list);
> - spin_unlock_irqrestore(&all_workqueue_stat[cpu].lock, flags);
> + list_add_tail(&cws->list, &workqueue_cpu_stat(cpu)->list);
> + spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
> }
>
> /* Destruction of a cpu workqueue thread */
> @@ -119,8 +121,8 @@ static void probe_workqueue_destruction(struct task_struct *wq_thread)
> struct cpu_workqueue_stats *node, *next;
> unsigned long flags;
>
> - spin_lock_irqsave(&all_workqueue_stat[cpu].lock, flags);
> - list_for_each_entry_safe(node, next, &all_workqueue_stat[cpu].list,
> + spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
> + list_for_each_entry_safe(node, next, &workqueue_cpu_stat(cpu)->list,
> list) {
> if (node->pid == wq_thread->pid) {
> list_del(&node->list);
> @@ -131,7 +133,7 @@ static void probe_workqueue_destruction(struct task_struct *wq_thread)
>
> pr_debug("trace_workqueue: don't find workqueue to destroy\n");
> found:
> - spin_unlock_irqrestore(&all_workqueue_stat[cpu].lock, flags);
> + spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
>
> }
>
> @@ -141,13 +143,13 @@ static struct cpu_workqueue_stats *workqueue_stat_start_cpu(int cpu)
> struct cpu_workqueue_stats *ret = NULL;
>
>
> - spin_lock_irqsave(&all_workqueue_stat[cpu].lock, flags);
> + spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
>
> - if (!list_empty(&all_workqueue_stat[cpu].list))
> - ret = list_entry(all_workqueue_stat[cpu].list.next,
> + if (!list_empty(&workqueue_cpu_stat(cpu)->list))
> + ret = list_entry(workqueue_cpu_stat(cpu)->list.next,
> struct cpu_workqueue_stats, list);
>
> - spin_unlock_irqrestore(&all_workqueue_stat[cpu].lock, flags);
> + spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
>
> return ret;
> }
> @@ -172,9 +174,9 @@ static void *workqueue_stat_next(void *prev, int idx)
> unsigned long flags;
> void *ret = NULL;
>
> - spin_lock_irqsave(&all_workqueue_stat[cpu].lock, flags);
> - if (list_is_last(&prev_cws->list, &all_workqueue_stat[cpu].list)) {
> - spin_unlock_irqrestore(&all_workqueue_stat[cpu].lock, flags);
> + spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
> + if (list_is_last(&prev_cws->list, &workqueue_cpu_stat(cpu)->list)) {
> + spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
> for (++cpu ; cpu < num_possible_cpus(); cpu++) {
> ret = workqueue_stat_start_cpu(cpu);
> if (ret)
> @@ -182,7 +184,7 @@ static void *workqueue_stat_next(void *prev, int idx)
> }
> return NULL;
> }
> - spin_unlock_irqrestore(&all_workqueue_stat[cpu].lock, flags);
> + spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
>
> return list_entry(prev_cws->list.next, struct cpu_workqueue_stats,
> list);
> @@ -199,10 +201,10 @@ static int workqueue_stat_show(struct seq_file *s, void *p)
> cws->executed,
> trace_find_cmdline(cws->pid));
>
> - spin_lock_irqsave(&all_workqueue_stat[cpu].lock, flags);
> - if (&cws->list == all_workqueue_stat[cpu].list.next)
> + spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
> + if (&cws->list == workqueue_cpu_stat(cpu)->list.next)
> seq_printf(s, "\n");
> - spin_unlock_irqrestore(&all_workqueue_stat[cpu].lock, flags);
> + spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
>
> return 0;
> }
> @@ -258,8 +260,7 @@ int __init trace_workqueue_early_init(void)
> if (ret)
> goto no_creation;
>
> - all_workqueue_stat = kmalloc(sizeof(struct workqueue_global_stats)
> - * num_possible_cpus(), GFP_KERNEL);
> + all_workqueue_stat = alloc_percpu(struct workqueue_global_stats);
>
> if (!all_workqueue_stat) {
> pr_warning("trace_workqueue: not enough memory\n");
> @@ -267,8 +268,8 @@ int __init trace_workqueue_early_init(void)
> }
>
> for_each_possible_cpu(cpu) {
> - spin_lock_init(&all_workqueue_stat[cpu].lock);
> - INIT_LIST_HEAD(&all_workqueue_stat[cpu].list);
> + spin_lock_init(&workqueue_cpu_stat(cpu)->lock);
> + INIT_LIST_HEAD(&workqueue_cpu_stat(cpu)->list);
> }
>
> return 0;
>
>
>