drivers/block: WQ_PERCPU added to alloc_workqueue users

Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.
This lack of consistentcy cannot be addressed without refactoring the API.

alloc_workqueue() treats all queues as per-CPU by default, while unbound
workqueues must opt-in via WQ_UNBOUND.

This default is suboptimal: most workloads benefit from unbound queues,
allowing the scheduler to place worker threads where they’re needed and
reducing noise when CPUs are isolated.

This default is suboptimal: most workloads benefit from unbound queues,
allowing the scheduler to place worker threads where they’re needed and
reducing noise when CPUs are isolated.

This patch adds a new WQ_PERCPU flag to explicitly request the use of
the per-CPU behavior. Both flags coexist for one release cycle to allow
callers to transition their calls.

Once migration is complete, WQ_UNBOUND can be removed and unbound will
become the implicit default.

With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND),
any alloc_workqueue() caller that doesn’t explicitly specify WQ_UNBOUND
must now use WQ_PERCPU.

All existing users have been updated accordingly.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/aoe/aoemain.c b/drivers/block/aoe/aoemain.c
index cdf6e4041bb924792d5b3019a6d481a58c61fa77..3b21750038ee8e5c072d35e3107a808f6b8dbab7 100644 (file)
--- a/drivers/block/aoe/aoemain.c
+++ b/drivers/block/aoe/aoemain.c
@@ -44,7 +44,7 @@ aoe_init(void)
 {
        int ret;
 
-       aoe_wq = alloc_workqueue("aoe_wq", 0, 0);
+       aoe_wq = alloc_workqueue("aoe_wq", WQ_PERCPU, 0);
        if (!aoe_wq)
                return -ENOMEM;
 

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index faafd7ff43d6ef53110ab3663cc7ac322214cc8c..af0e21149dbc9e2230ccdc624ae3616448c23d51 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -7389,7 +7389,7 @@ static int __init rbd_init(void)
         * The number of active work items is limited by the number of
         * rbd devices * queue depth, so leave @max_active at default.
         */
-       rbd_wq = alloc_workqueue(RBD_DRV_NAME, WQ_MEM_RECLAIM, 0);
+       rbd_wq = alloc_workqueue(RBD_DRV_NAME, WQ_MEM_RECLAIM | WQ_PERCPU, 0);
        if (!rbd_wq) {
                rc = -ENOMEM;
                goto err_out_slab;

diff --git a/drivers/block/rnbd/rnbd-clt.c b/drivers/block/rnbd/rnbd-clt.c
index 119b7e27023f96ca62dc47d730b5b585a01235cd..f1409e54010a67ec3da8b00b8dd5341c7f5d995e 100644 (file)
--- a/drivers/block/rnbd/rnbd-clt.c
+++ b/drivers/block/rnbd/rnbd-clt.c
@@ -1809,7 +1809,7 @@ static int __init rnbd_client_init(void)
                unregister_blkdev(rnbd_client_major, "rnbd");
                return err;
        }
-       rnbd_clt_wq = alloc_workqueue("rnbd_clt_wq", 0, 0);
+       rnbd_clt_wq = alloc_workqueue("rnbd_clt_wq", WQ_PERCPU, 0);
        if (!rnbd_clt_wq) {
                pr_err("Failed to load module, alloc_workqueue failed.\n");
                rnbd_clt_destroy_sysfs_files();

diff --git a/drivers/block/sunvdc.c b/drivers/block/sunvdc.c
index 3ab46bb0c23dbd5bca09b51db4786d68d8d93bb4..db1fe9772a4d7404c2797bac45b657c7f7553132 100644 (file)
--- a/drivers/block/sunvdc.c
+++ b/drivers/block/sunvdc.c
@@ -1216,7 +1216,7 @@ static int __init vdc_init(void)
 {
        int err;
 
-       sunvdc_wq = alloc_workqueue("sunvdc", 0, 0);
+       sunvdc_wq = alloc_workqueue("sunvdc", WQ_PERCPU, 0);
        if (!sunvdc_wq)
                return -ENOMEM;
 

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 85efa7e535f8ba4db358ed74cc9a71aff4631639..f061420dfb10c40b21765b173fab7046aa447506 100644 (file)
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -1682,7 +1682,7 @@ static int __init virtio_blk_init(void)
 {
        int error;
 
-       virtblk_wq = alloc_workqueue("virtio-blk", 0, 0);
+       virtblk_wq = alloc_workqueue("virtio-blk", WQ_PERCPU, 0);
        if (!virtblk_wq)
                return -ENOMEM;