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Message-ID: <20130124193944.GR2373@mtj.dyndns.org>
Date: Thu, 24 Jan 2013 11:39:44 -0800
From: Tejun Heo <tj@...nel.org>
To: Joonsoo Kim <js1304@...il.com>,
Lai Jiangshan <laijs@...fujitsu.com>
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH wq/for-3.9] workqueue: move nr_running into worker_pool
As nr_running is likely to be accessed from other CPUs during
try_to_wake_up(), it was kept outside worker_pool; however, while less
frequent, other fields in worker_pool are accessed from other CPUs
for, e.g., non-reentrancy check. Also, with recent pool related
changes, accessing nr_running matching the worker_pool isn't as simple
as it used to be.
Move nr_running inside worker_pool. Keep it aligned to cacheline and
define CPU pools using DEFINE_PER_CPU_SHARED_ALIGNED(). This should
give at least the same cacheline behavior.
get_pool_nr_running() is replaced with direct pool->nr_running
accesses.
Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Joonsoo Kim <js1304@...il.com>
---
kernel/workqueue.c | 63 ++++++++++++++++++-----------------------------------
1 file changed, 22 insertions(+), 41 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 577de10..a49cc88 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -144,6 +144,13 @@ struct worker_pool {
struct mutex assoc_mutex; /* protect POOL_DISASSOCIATED */
struct ida worker_ida; /* L: for worker IDs */
+
+ /*
+ * The current concurrency level. As it's likely to be accessed
+ * from other CPUs during try_to_wake_up(), put it in a separate
+ * cacheline.
+ */
+ atomic_t nr_running ____cacheline_aligned_in_smp;
} ____cacheline_aligned_in_smp;
/*
@@ -417,23 +424,12 @@ static LIST_HEAD(workqueues);
static bool workqueue_freezing; /* W: have wqs started freezing? */
/*
- * The CPU standard worker pools. nr_running is the only field which is
- * expected to be used frequently by other cpus via try_to_wake_up(). Put
- * it in a separate cacheline.
- */
-static DEFINE_PER_CPU(struct worker_pool [NR_STD_WORKER_POOLS],
- cpu_std_worker_pools);
-static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t [NR_STD_WORKER_POOLS],
- cpu_std_pool_nr_running);
-
-/*
- * Standard worker pools and nr_running counter for unbound CPU. The pools
- * have POOL_DISASSOCIATED set, and all workers have WORKER_UNBOUND set.
+ * The CPU and unbound standard worker pools. The unbound ones have
+ * POOL_DISASSOCIATED set, and their workers have WORKER_UNBOUND set.
*/
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS],
+ cpu_std_worker_pools);
static struct worker_pool unbound_std_worker_pools[NR_STD_WORKER_POOLS];
-static atomic_t unbound_std_pool_nr_running[NR_STD_WORKER_POOLS] = {
- [0 ... NR_STD_WORKER_POOLS - 1] = ATOMIC_INIT(0), /* always 0 */
-};
/* idr of all pools */
static DEFINE_MUTEX(worker_pool_idr_mutex);
@@ -483,17 +479,6 @@ static struct worker_pool *get_std_worker_pool(int cpu, bool highpri)
return &pools[highpri];
}
-static atomic_t *get_pool_nr_running(struct worker_pool *pool)
-{
- int cpu = pool->cpu;
- int idx = std_worker_pool_pri(pool);
-
- if (cpu != WORK_CPU_UNBOUND)
- return &per_cpu(cpu_std_pool_nr_running, cpu)[idx];
- else
- return &unbound_std_pool_nr_running[idx];
-}
-
static struct cpu_workqueue_struct *get_cwq(unsigned int cpu,
struct workqueue_struct *wq)
{
@@ -647,7 +632,7 @@ static bool work_is_canceling(struct work_struct *work)
static bool __need_more_worker(struct worker_pool *pool)
{
- return !atomic_read(get_pool_nr_running(pool));
+ return !atomic_read(&pool->nr_running);
}
/*
@@ -672,9 +657,8 @@ static bool may_start_working(struct worker_pool *pool)
/* Do I need to keep working? Called from currently running workers. */
static bool keep_working(struct worker_pool *pool)
{
- atomic_t *nr_running = get_pool_nr_running(pool);
-
- return !list_empty(&pool->worklist) && atomic_read(nr_running) <= 1;
+ return !list_empty(&pool->worklist) &&
+ atomic_read(&pool->nr_running) <= 1;
}
/* Do we need a new worker? Called from manager. */
@@ -754,7 +738,7 @@ void wq_worker_waking_up(struct task_struct *task, unsigned int cpu)
if (!(worker->flags & WORKER_NOT_RUNNING)) {
WARN_ON_ONCE(worker->pool->cpu != cpu);
- atomic_inc(get_pool_nr_running(worker->pool));
+ atomic_inc(&worker->pool->nr_running);
}
}
@@ -778,7 +762,6 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task,
{
struct worker *worker = kthread_data(task), *to_wakeup = NULL;
struct worker_pool *pool;
- atomic_t *nr_running;
/*
* Rescuers, which may not have all the fields set up like normal
@@ -789,7 +772,6 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task,
return NULL;
pool = worker->pool;
- nr_running = get_pool_nr_running(pool);
/* this can only happen on the local cpu */
BUG_ON(cpu != raw_smp_processor_id());
@@ -805,7 +787,8 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task,
* manipulating idle_list, so dereferencing idle_list without pool
* lock is safe.
*/
- if (atomic_dec_and_test(nr_running) && !list_empty(&pool->worklist))
+ if (atomic_dec_and_test(&pool->nr_running) &&
+ !list_empty(&pool->worklist))
to_wakeup = first_worker(pool);
return to_wakeup ? to_wakeup->task : NULL;
}
@@ -837,14 +820,12 @@ static inline void worker_set_flags(struct worker *worker, unsigned int flags,
*/
if ((flags & WORKER_NOT_RUNNING) &&
!(worker->flags & WORKER_NOT_RUNNING)) {
- atomic_t *nr_running = get_pool_nr_running(pool);
-
if (wakeup) {
- if (atomic_dec_and_test(nr_running) &&
+ if (atomic_dec_and_test(&pool->nr_running) &&
!list_empty(&pool->worklist))
wake_up_worker(pool);
} else
- atomic_dec(nr_running);
+ atomic_dec(&pool->nr_running);
}
worker->flags |= flags;
@@ -876,7 +857,7 @@ static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
*/
if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
if (!(worker->flags & WORKER_NOT_RUNNING))
- atomic_inc(get_pool_nr_running(pool));
+ atomic_inc(&pool->nr_running);
}
/**
@@ -1540,7 +1521,7 @@ static void worker_enter_idle(struct worker *worker)
*/
WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
pool->nr_workers == pool->nr_idle &&
- atomic_read(get_pool_nr_running(pool)));
+ atomic_read(&pool->nr_running));
}
/**
@@ -3538,7 +3519,7 @@ static void wq_unbind_fn(struct work_struct *work)
* didn't already.
*/
for_each_std_worker_pool(pool, cpu)
- atomic_set(get_pool_nr_running(pool), 0);
+ atomic_set(&pool->nr_running, 0);
}
/*
--
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