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Subject[PATCH] workqueue: don't alloc_percpu for single workqueue

allocating memory for every cpu for single workqueue is waste.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 2f44583..ecd693d 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -99,7 +99,7 @@ static
struct cpu_workqueue_struct *wq_per_cpu(struct workqueue_struct *wq, int cpu)
{
if (unlikely(is_wq_single_threaded(wq)))
- cpu = singlethread_cpu;
+ return wq->cpu_wq;
return per_cpu_ptr(wq->cpu_wq, cpu);
}

@@ -417,7 +417,7 @@ void flush_workqueue(struct workqueue_struct *wq)
lock_map_acquire(&wq->lockdep_map);
lock_map_release(&wq->lockdep_map);
for_each_cpu_mask_nr(cpu, *cpu_map)
- flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
+ flush_cpu_workqueue(wq_per_cpu(wq, cpu));
}
EXPORT_SYMBOL_GPL(flush_workqueue);

@@ -548,7 +548,7 @@ static void wait_on_work(struct work_struct *work)
cpu_map = wq_cpu_map(wq);

for_each_cpu_mask_nr(cpu, *cpu_map)
- wait_on_cpu_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
+ wait_on_cpu_work(wq_per_cpu(wq, cpu), work);
}

static int __cancel_work_timer(struct work_struct *work,
@@ -752,17 +752,13 @@ int current_is_keventd(void)

}

-static struct cpu_workqueue_struct *
-init_cpu_workqueue(struct workqueue_struct *wq, int cpu)
+static void init_cpu_workqueue(struct workqueue_struct *wq,
+ struct cpu_workqueue_struct *cwq)
{
- struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
-
cwq->wq = wq;
spin_lock_init(&cwq->lock);
INIT_LIST_HEAD(&cwq->worklist);
init_waitqueue_head(&cwq->more_work);
-
- return cwq;
}

static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
@@ -816,7 +812,10 @@ struct workqueue_struct *__create_workqueue_key(const char *name,
if (!wq)
return NULL;

- wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
+ if (singlethread)
+ wq->cpu_wq = kmalloc(sizeof(*cwq), GFP_KERNEL);
+ else
+ wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
if (!wq->cpu_wq) {
kfree(wq);
return NULL;
@@ -830,7 +829,8 @@ struct workqueue_struct *__create_workqueue_key(const char *name,
INIT_LIST_HEAD(&wq->list);

if (singlethread) {
- cwq = init_cpu_workqueue(wq, singlethread_cpu);
+ cwq = wq->cpu_wq;
+ init_cpu_workqueue(wq, cwq);
err = create_workqueue_thread(cwq, singlethread_cpu);
start_workqueue_thread(cwq, -1);
} else {
@@ -851,7 +851,8 @@ struct workqueue_struct *__create_workqueue_key(const char *name,
* lock.
*/
for_each_possible_cpu(cpu) {
- cwq = init_cpu_workqueue(wq, cpu);
+ cwq = per_cpu_ptr(wq->cpu_wq, cpu);
+ init_cpu_workqueue(wq, cwq);
if (err || !cpu_online(cpu))
continue;
err = create_workqueue_thread(cwq, cpu);
@@ -906,6 +907,13 @@ void destroy_workqueue(struct workqueue_struct *wq)
const struct cpumask *cpu_map = wq_cpu_map(wq);
int cpu;

+ if (is_wq_single_threaded(wq)) {
+ cleanup_workqueue_thread(wq->cpu_wq);
+ kfree(wq->cpu_wq);
+ kfree(wq);
+ return;
+ }
+
cpu_maps_update_begin();
spin_lock(&workqueue_lock);
list_del(&wq->list);



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