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workqueue: map an unbound workqueues to multiple per-node pool_workqueues

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Currently, an unbound workqueue has only one "current" pool_workqueue
associated with it.  It may have multple pool_workqueues but only the
first pool_workqueue servies new work items.  For NUMA affinity, we
want to change this so that there are multiple current pool_workqueues
serving different NUMA nodes.

Introduce workqueue->numa_pwq_tbl[] which is indexed by NUMA node and
points to the pool_workqueue to use for each possible node.  This
replaces first_pwq() in __queue_work() and workqueue_congested().

numa_pwq_tbl[] is currently initialized to point to the same
pool_workqueue as first_pwq() so this patch doesn't make any behavior
changes.

v2: Use rcu_dereference_raw() in unbound_pwq_by_node() as the function
    may be called only with wq->mutex held.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
This commit is contained in:
Tejun Heo 2013-04-01 11:23:35 -07:00
parent 2728fd2f09
commit df2d5ae499
1 changed files with 37 additions and 11 deletions
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48
kernel/workqueue.c
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@ -257,6 +257,7 @@ struct workqueue_struct {
/* hot fields used during command issue, aligned to cacheline */
unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */
struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
struct pool_workqueue __rcu *numa_pwq_tbl[]; /* FR: unbound pwqs indexed by node */
};
static struct kmem_cache *pwq_cache;
@ -525,6 +526,22 @@ static struct pool_workqueue *first_pwq(struct workqueue_struct *wq)
pwqs_node);
}
/**
* unbound_pwq_by_node - return the unbound pool_workqueue for the given node
* @wq: the target workqueue
* @node: the node ID
*
* This must be called either with pwq_lock held or sched RCU read locked.
* If the pwq needs to be used beyond the locking in effect, the caller is
* responsible for guaranteeing that the pwq stays online.
*/
static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
int node)
{
assert_rcu_or_wq_mutex(wq);
return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
}
static unsigned int work_color_to_flags(int color)
{
return color << WORK_STRUCT_COLOR_SHIFT;
@ -1278,14 +1295,14 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
WARN_ON_ONCE(!is_chained_work(wq)))
return;
retry:
if (req_cpu == WORK_CPU_UNBOUND)
cpu = raw_smp_processor_id();
/* pwq which will be used unless @work is executing elsewhere */
if (!(wq->flags & WQ_UNBOUND)) {
if (cpu == WORK_CPU_UNBOUND)
cpu = raw_smp_processor_id();
if (!(wq->flags & WQ_UNBOUND))
pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
} else {
pwq = first_pwq(wq);
}
else
pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
/*
* If @work was previously on a different pool, it might still be
@ -1315,8 +1332,8 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
* pwq is determined and locked. For unbound pools, we could have
* raced with pwq release and it could already be dead. If its
* refcnt is zero, repeat pwq selection. Note that pwqs never die
* without another pwq replacing it as the first pwq or while a
* work item is executing on it, so the retying is guaranteed to
* without another pwq replacing it in the numa_pwq_tbl or while
* work items are executing on it, so the retrying is guaranteed to
* make forward-progress.
*/
if (unlikely(!pwq->refcnt)) {
@ -3614,6 +3631,8 @@ static void init_and_link_pwq(struct pool_workqueue *pwq,
struct worker_pool *pool,
struct pool_workqueue **p_last_pwq)
{
int node;
BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
pwq->pool = pool;
@ -3640,8 +3659,11 @@ static void init_and_link_pwq(struct pool_workqueue *pwq,
/* link in @pwq */
list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
if (wq->flags & WQ_UNBOUND)
if (wq->flags & WQ_UNBOUND) {
copy_workqueue_attrs(wq->unbound_attrs, pool->attrs);
for_each_node(node)
rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
}
mutex_unlock(&wq->mutex);
}
@ -3761,12 +3783,16 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
struct lock_class_key *key,
const char *lock_name, ...)
{
size_t tbl_size = 0;
va_list args;
struct workqueue_struct *wq;
struct pool_workqueue *pwq;
/* allocate wq and format name */
wq = kzalloc(sizeof(*wq), GFP_KERNEL);
if (flags & WQ_UNBOUND)
tbl_size = wq_numa_tbl_len * sizeof(wq->numa_pwq_tbl[0]);
wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL);
if (!wq)
return NULL;
@ -3994,7 +4020,7 @@ bool workqueue_congested(int cpu, struct workqueue_struct *wq)
if (!(wq->flags & WQ_UNBOUND))
pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
else
pwq = first_pwq(wq);
pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
ret = !list_empty(&pwq->delayed_works);
rcu_read_unlock_sched();