[RFC v2 4/7] workqueue: use new hashtable implementation

Sasha Levin
2012-08-03T14:23:05Z

Switch workqueues to use the new hashtable implementation. This reduces the amount of
generic unrelated code in the workqueues.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
kernel/workqueue.c | 93 ++++++++--------------------------------------------
1 files changed, 14 insertions(+), 79 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 692d976..480975d 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -41,6 +41,7 @@
#include <linux/debug_locks.h>
#include <linux/lockdep.h>
#include <linux/idr.h>
+#include <linux/hashtable.h>

#include "workqueue_sched.h"

@@ -82,8 +83,6 @@ enum {
NR_WORKER_POOLS = 2, /* # worker pools per gcwq */

BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
- BUSY_WORKER_HASH_SIZE = 1 << BUSY_WORKER_HASH_ORDER,
- BUSY_WORKER_HASH_MASK = BUSY_WORKER_HASH_SIZE - 1,

MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
@@ -102,6 +101,8 @@ enum {
HIGHPRI_NICE_LEVEL = -20,
};

+#define worker_hash_cmp(obj, key) ((obj)->current_work == (key))
+
/*
* Structure fields follow one of the following exclusion rules.
*
@@ -180,7 +181,7 @@ struct global_cwq {
unsigned int flags; /* L: GCWQ_* flags */

/* workers are chained either in busy_hash or pool idle_list */
- struct hlist_head busy_hash[BUSY_WORKER_HASH_SIZE];
+ DEFINE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
/* L: hash of busy workers */

struct worker_pool pools[2]; /* normal and highpri pools */
@@ -287,10 +288,6 @@ EXPORT_SYMBOL_GPL(system_nrt_freezable_wq);
for ((pool) = &(gcwq)->pools[0]; \
(pool) < &(gcwq)->pools[NR_WORKER_POOLS]; (pool)++)

-#define for_each_busy_worker(worker, i, pos, gcwq) \
- for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) \
- hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry)
-
static inline int __next_gcwq_cpu(int cpu, const struct cpumask *mask,
unsigned int sw)
{
@@ -822,70 +819,11 @@ static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
}

/**
- * busy_worker_head - return the busy hash head for a work
- * @gcwq: gcwq of interest
- * @work: work to be hashed
- *
- * Return hash head of @gcwq for @work.
- *
- * CONTEXT:
- * spin_lock_irq(gcwq->lock).
- *
- * RETURNS:
- * Pointer to the hash head.
- */
-static struct hlist_head *busy_worker_head(struct global_cwq *gcwq,
- struct work_struct *work)
-{
- const int base_shift = ilog2(sizeof(struct work_struct));
- unsigned long v = (unsigned long)work;
-
- /* simple shift and fold hash, do we need something better? */
- v >>= base_shift;
- v += v >> BUSY_WORKER_HASH_ORDER;
- v &= BUSY_WORKER_HASH_MASK;
-
- return &gcwq->busy_hash[v];
-}
-
-/**
- * __find_worker_executing_work - find worker which is executing a work
- * @gcwq: gcwq of interest
- * @bwh: hash head as returned by busy_worker_head()
- * @work: work to find worker for
- *
- * Find a worker which is executing @work on @gcwq. @bwh should be
- * the hash head obtained by calling busy_worker_head() with the same
- * work.
- *
- * CONTEXT:
- * spin_lock_irq(gcwq->lock).
- *
- * RETURNS:
- * Pointer to worker which is executing @work if found, NULL
- * otherwise.
- */
-static struct worker *__find_worker_executing_work(struct global_cwq *gcwq,
- struct hlist_head *bwh,
- struct work_struct *work)
-{
- struct worker *worker;
- struct hlist_node *tmp;
-
- hlist_for_each_entry(worker, tmp, bwh, hentry)
- if (worker->current_work == work)
- return worker;
- return NULL;
-}
-
-/**
* find_worker_executing_work - find worker which is executing a work
* @gcwq: gcwq of interest
* @work: work to find worker for
*
- * Find a worker which is executing @work on @gcwq. This function is
- * identical to __find_worker_executing_work() except that this
- * function calculates @bwh itself.
+ * Find a worker which is executing @work on @gcwq.
*
* CONTEXT:
* spin_lock_irq(gcwq->lock).
@@ -897,8 +835,8 @@ static struct worker *__find_worker_executing_work(struct global_cwq *gcwq,
static struct worker *find_worker_executing_work(struct global_cwq *gcwq,
struct work_struct *work)
{
- return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work),
- work);
+ return hash_get(&gcwq->busy_hash, work, struct worker,
+ hentry, worker_hash_cmp);
}

/**
@@ -959,7 +897,7 @@ static bool is_chained_work(struct workqueue_struct *wq)
int i;

spin_lock_irqsave(&gcwq->lock, flags);
- for_each_busy_worker(worker, i, pos, gcwq) {
+ hash_for_each(i, pos, &gcwq->busy_hash, worker, hentry) {
if (worker->task != current)
continue;
spin_unlock_irqrestore(&gcwq->lock, flags);
@@ -1432,7 +1370,7 @@ retry:
wake_up_all(&gcwq->rebind_hold);

/* rebind busy workers */
- for_each_busy_worker(worker, i, pos, gcwq) {
+ hash_for_each(i, pos, &gcwq->busy_hash, worker, hentry) {
struct work_struct *rebind_work = &worker->rebind_work;

/* morph UNBOUND to REBIND */
@@ -1932,7 +1870,6 @@ __acquires(&gcwq->lock)
struct cpu_workqueue_struct *cwq = get_work_cwq(work);
struct worker_pool *pool = worker->pool;
struct global_cwq *gcwq = pool->gcwq;
- struct hlist_head *bwh = busy_worker_head(gcwq, work);
bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE;
work_func_t f = work->func;
int work_color;
@@ -1964,7 +1901,7 @@ __acquires(&gcwq->lock)
* already processing the work. If so, defer the work to the
* currently executing one.
*/
- collision = __find_worker_executing_work(gcwq, bwh, work);
+ collision = find_worker_executing_work(gcwq, work);
if (unlikely(collision)) {
move_linked_works(work, &collision->scheduled, NULL);
return;
@@ -1972,7 +1909,7 @@ __acquires(&gcwq->lock)

/* claim and process */
debug_work_deactivate(work);
- hlist_add_head(&worker->hentry, bwh);
+ hash_add(&gcwq->busy_hash, &worker->hentry, (long)work);
worker->current_work = work;
worker->current_cwq = cwq;
work_color = get_work_color(work);
@@ -2027,7 +1964,7 @@ __acquires(&gcwq->lock)
worker_clr_flags(worker, WORKER_CPU_INTENSIVE);

/* we're done with it, release */
- hlist_del_init(&worker->hentry);
+ hash_del(&worker->hentry);
worker->current_work = NULL;
worker->current_cwq = NULL;
cwq_dec_nr_in_flight(cwq, work_color, false);
@@ -3405,7 +3342,7 @@ static void gcwq_unbind_fn(struct work_struct *work)
list_for_each_entry(worker, &pool->idle_list, entry)
worker->flags |= WORKER_UNBOUND;

- for_each_busy_worker(worker, i, pos, gcwq)
+ hash_for_each(i, pos, &gcwq->busy_hash, worker, hentry)
worker->flags |= WORKER_UNBOUND;

gcwq->flags |= GCWQ_DISASSOCIATED;
@@ -3690,7 +3627,6 @@ out_unlock:
static int __init init_workqueues(void)
{
unsigned int cpu;
- int i;

cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);
cpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);
@@ -3704,8 +3640,7 @@ static int __init init_workqueues(void)
gcwq->cpu = cpu;
gcwq->flags |= GCWQ_DISASSOCIATED;

- for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)
- INIT_HLIST_HEAD(&gcwq->busy_hash[i]);
+ hash_init(&gcwq->busy_hash, BUSY_WORKER_HASH_ORDER);

for_each_worker_pool(pool, gcwq) {
pool->gcwq = gcwq;
--
1.7.8.6