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workqueue: make get_work_pool_id() cheaper

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get_work_pool_id() currently first obtains pool using get_work_pool()
and then return pool->id.  For an off-queue work item, this involves
obtaining pool ID from worker->data, performing idr_find() to find the
matching pool and then returning its pool->id which of course is the
same as the one which went into idr_find().

Just open code WORK_STRUCT_CWQ case and directly return pool ID from
work->data.

tj: The original patch dropped on-queue work item handling and renamed
    the function to offq_work_pool_id().  There isn't much benefit in
    doing so.  Handling it only requires a single if() and we need at
    least BUG_ON(), which is also a branch, even if we drop on-queue
    handling.  Open code WORK_STRUCT_CWQ case and keep the function in
    line with get_work_pool().  Rewrote the description.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Lai Jiangshan 2013-02-07 13:14:20 -08:00 committed by Tejun Heo
parent e19e397a85
commit 54d5b7d079
1 changed files with 6 additions and 2 deletions
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8
kernel/workqueue.c
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@ -611,9 +611,13 @@ static struct worker_pool *get_work_pool(struct work_struct *work)
*/
static int get_work_pool_id(struct work_struct *work)
{
struct worker_pool *pool = get_work_pool(work);
unsigned long data = atomic_long_read(&work->data);
return pool ? pool->id : WORK_OFFQ_POOL_NONE;
if (data & WORK_STRUCT_CWQ)
return ((struct cpu_workqueue_struct *)
(data & WORK_STRUCT_WQ_DATA_MASK))->pool->id;
return data >> WORK_OFFQ_POOL_SHIFT;
}
static void mark_work_canceling(struct work_struct *work)