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authorMing Lei <ming.lei@canonical.com>2015-08-17 05:31:48 +0300
committerJens Axboe <axboe@fb.com>2015-09-23 20:01:16 +0300
commite03a3d7a94e2485b6e2fa3fb630b9b3a30b65718 (patch)
treece0d022f49faefa5845da085c0dcd66ff72252f9 /drivers/block/loop.c
parent5b5e20f421c0b6d437b3dec13e53674161998d56 (diff)
downloadlinux-e03a3d7a94e2485b6e2fa3fb630b9b3a30b65718.tar.xz
block: loop: use kthread_work
The following patch will use dio/aio to submit IO to backing file, then it needn't to schedule IO concurrently from work, so use kthread_work for decreasing context switch cost a lot. For non-AIO case, single thread has been used for long long time, and it was just converted to work in v4.0, which has caused performance regression for fedora live booting already. In discussion[1], even though submitting I/O via work concurrently can improve random read IO throughput, meantime it might hurt sequential read IO performance, so better to restore to single thread behaviour. For the following AIO support, it is better to use multi hw-queue with per-hwq kthread than current work approach suppose there is so high performance requirement for loop. [1] http://marc.info/?t=143082678400002&r=1&w=2 Signed-off-by: Ming Lei <ming.lei@canonical.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'drivers/block/loop.c')
-rw-r--r--drivers/block/loop.c79
1 files changed, 24 insertions, 55 deletions
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index eee751032cad..1875aadb31b0 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -688,6 +688,23 @@ static void loop_config_discard(struct loop_device *lo)
queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
}
+static void loop_unprepare_queue(struct loop_device *lo)
+{
+ flush_kthread_worker(&lo->worker);
+ kthread_stop(lo->worker_task);
+}
+
+static int loop_prepare_queue(struct loop_device *lo)
+{
+ init_kthread_worker(&lo->worker);
+ lo->worker_task = kthread_run(kthread_worker_fn,
+ &lo->worker, "loop%d", lo->lo_number);
+ if (IS_ERR(lo->worker_task))
+ return -ENOMEM;
+ set_user_nice(lo->worker_task, MIN_NICE);
+ return 0;
+}
+
static int loop_set_fd(struct loop_device *lo, fmode_t mode,
struct block_device *bdev, unsigned int arg)
{
@@ -745,11 +762,8 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
size = get_loop_size(lo, file);
if ((loff_t)(sector_t)size != size)
goto out_putf;
- error = -ENOMEM;
- lo->wq = alloc_workqueue("kloopd%d",
- WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_UNBOUND, 16,
- lo->lo_number);
- if (!lo->wq)
+ error = loop_prepare_queue(lo);
+ if (error)
goto out_putf;
error = 0;
@@ -903,8 +917,7 @@ static int loop_clr_fd(struct loop_device *lo)
lo->lo_flags = 0;
if (!part_shift)
lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
- destroy_workqueue(lo->wq);
- lo->wq = NULL;
+ loop_unprepare_queue(lo);
mutex_unlock(&lo->lo_ctl_mutex);
/*
* Need not hold lo_ctl_mutex to fput backing file.
@@ -1461,23 +1474,7 @@ static int loop_queue_rq(struct blk_mq_hw_ctx *hctx,
if (lo->lo_state != Lo_bound)
return -EIO;
- if (cmd->rq->cmd_flags & REQ_WRITE) {
- struct loop_device *lo = cmd->rq->q->queuedata;
- bool need_sched = true;
-
- spin_lock_irq(&lo->lo_lock);
- if (lo->write_started)
- need_sched = false;
- else
- lo->write_started = true;
- list_add_tail(&cmd->list, &lo->write_cmd_head);
- spin_unlock_irq(&lo->lo_lock);
-
- if (need_sched)
- queue_work(lo->wq, &lo->write_work);
- } else {
- queue_work(lo->wq, &cmd->read_work);
- }
+ queue_kthread_work(&lo->worker, &cmd->work);
return BLK_MQ_RQ_QUEUE_OK;
}
@@ -1499,35 +1496,10 @@ static void loop_handle_cmd(struct loop_cmd *cmd)
blk_mq_complete_request(cmd->rq);
}
-static void loop_queue_write_work(struct work_struct *work)
-{
- struct loop_device *lo =
- container_of(work, struct loop_device, write_work);
- LIST_HEAD(cmd_list);
-
- spin_lock_irq(&lo->lo_lock);
- repeat:
- list_splice_init(&lo->write_cmd_head, &cmd_list);
- spin_unlock_irq(&lo->lo_lock);
-
- while (!list_empty(&cmd_list)) {
- struct loop_cmd *cmd = list_first_entry(&cmd_list,
- struct loop_cmd, list);
- list_del_init(&cmd->list);
- loop_handle_cmd(cmd);
- }
-
- spin_lock_irq(&lo->lo_lock);
- if (!list_empty(&lo->write_cmd_head))
- goto repeat;
- lo->write_started = false;
- spin_unlock_irq(&lo->lo_lock);
-}
-
-static void loop_queue_read_work(struct work_struct *work)
+static void loop_queue_work(struct kthread_work *work)
{
struct loop_cmd *cmd =
- container_of(work, struct loop_cmd, read_work);
+ container_of(work, struct loop_cmd, work);
loop_handle_cmd(cmd);
}
@@ -1539,7 +1511,7 @@ static int loop_init_request(void *data, struct request *rq,
struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);
cmd->rq = rq;
- INIT_WORK(&cmd->read_work, loop_queue_read_work);
+ init_kthread_work(&cmd->work, loop_queue_work);
return 0;
}
@@ -1601,9 +1573,6 @@ static int loop_add(struct loop_device **l, int i)
*/
queue_flag_set_unlocked(QUEUE_FLAG_NOMERGES, lo->lo_queue);
- INIT_LIST_HEAD(&lo->write_cmd_head);
- INIT_WORK(&lo->write_work, loop_queue_write_work);
-
disk = lo->lo_disk = alloc_disk(1 << part_shift);
if (!disk)
goto out_free_queue;