[RFC PATCH net-next 0/5] net: Move system_long_wq to system_dfl_long_wq

[RFC PATCH net-next 0/5] net: Move system_long_wq to system_dfl_long_wq

[Marco Crivellari]

Hello,

Currently the code uses the per-cpu workqueue system_long_wq to schedule
long running works.

Unbound works could benefit from scheduler task placement, to optimize
performance and power consumption. Another good reason to have this unbound,
is the "queue_delayed_work()" function, used to enqueue the work item.
More details on this will follow in the next section.

Recently, a new unbound workqueue specific for long running work has been
added:

    c116737e972e ("workqueue: Add system_dfl_long_wq for long unbound works")

~~~ Details about queue_delayed_work ~~~

system_long_wq is a per-cpu workqueue and it is used as a parameter of
queue_delayed_work(). This function schedule an item that it will later
be enqueued (once the timer will fire). __queue_delayed_work() does the job
receiving as "cpu" WORK_CPU_UNBOUND:

    if (housekeeping_enabled(HK_TYPE_TIMER)) {
    //      [....]
    } else {
            if (likely(cpu == WORK_CPU_UNBOUND))
                    add_timer_global(timer);
            else
                    add_timer_on(timer, cpu);
    }

The timer is global, so can fire everywhere, and the work item will be
enqueued where the timer fired.

Since the workqueue work doesn't rely on per-cpu variables, there is no
obvious reason that justify the use of a per-cpu workqueue. So change the
workqueue with the new system_dfl_long_wq, so that the used workqueue is
now unbound and can benefit from scheduler task placement.

Thanks!

Marco Crivellari (5):
  ibmvnic: Move long delayed work on system_dfl_long_wq
  net: ti: icssg-stats: Move long delayed work on system_dfl_long_wq
  net: thunderbolt: Move long delayed work on system_dfl_long_wq
  net: usb: pegasus: Move long delayed work on system_dfl_long_wq
  r8152: Move long delayed work on system_dfl_long_wq

 drivers/net/ethernet/ibm/ibmvnic.c          | 4 ++--
 drivers/net/ethernet/ti/icssg/icssg_stats.c | 2 +-
 drivers/net/thunderbolt/main.c              | 7 ++++---
 drivers/net/usb/pegasus.c                   | 9 +++++----
 drivers/net/usb/r8152.c                     | 7 ++++---
 5 files changed, 16 insertions(+), 13 deletions(-)

-- 
2.54.0

[RFC PATCH net-next 1/5] ibmvnic: Move long delayed work on system_dfl_long_wq

[Marco Crivellari]

Currently the code enqueue work items using {queue|mod}_delayed_work(),
using system_long_wq. This workqueue should be used when long works are
expected and it is a per-cpu workqueue.

The function(s) end up calling __queue_delayed_work(), which set a global
timer that could fire anywhere, enqueuing the work where the timer fired.

Unbound works could benefit from scheduler task placement, to optimize
performance and power consumption. Long work shouldn't stick to a single
CPU.

Recently, a new unbound workqueue specific for long running work has
been added:

    c116737e972e ("workqueue: Add system_dfl_long_wq for long unbound works")

Since the workqueue work doesn't rely on per-cpu variables, there is no
obvious reason that justify the use of a per-cpu workqueue. So change
system_long_wq with system_dfl_long_wq so that the work may benefit from
scheduler task placement.

Cc: Haren Myneni <haren@linux.ibm.com>
Cc: Rick Lindsley <ricklind@linux.ibm.com>
Cc: Nick Child <nnac123@linux.ibm.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
 drivers/net/ethernet/ibm/ibmvnic.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 5a510eed335e..a1c01c9820d2 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -3229,7 +3229,7 @@ static void __ibmvnic_reset(struct work_struct *work)
 	if (adapter->state == VNIC_PROBING &&
 	    !wait_for_completion_timeout(&adapter->probe_done, timeout)) {
 		dev_err(dev, "Reset thread timed out on probe");
-		queue_delayed_work(system_long_wq,
+		queue_delayed_work(system_dfl_long_wq,
 				   &adapter->ibmvnic_delayed_reset,
 				   IBMVNIC_RESET_DELAY);
 		return;
@@ -3267,7 +3267,7 @@ static void __ibmvnic_reset(struct work_struct *work)
 	spin_lock(&adapter->rwi_lock);
 	if (!list_empty(&adapter->rwi_list)) {
 		if (test_and_set_bit_lock(0, &adapter->resetting)) {
-			queue_delayed_work(system_long_wq,
+			queue_delayed_work(system_dfl_long_wq,
 					   &adapter->ibmvnic_delayed_reset,
 					   IBMVNIC_RESET_DELAY);
 		} else {
-- 
2.54.0

[RFC PATCH net-next 2/5] net: ti: icssg-stats: Move long delayed work on system_dfl_long_wq

[Marco Crivellari]

Currently the code enqueue work items using {queue|mod}_delayed_work(),
using system_long_wq. This workqueue should be used when long works are
expected and it is a per-cpu workqueue.

The function(s) end up calling __queue_delayed_work(), which set a global
timer that could fire anywhere, enqueuing the work where the timer fired.

Unbound works could benefit from scheduler task placement, to optimize
performance and power consumption. Long work shouldn't stick to a single
CPU.

Recently, a new unbound workqueue specific for long running work has
been added:

    c116737e972e ("workqueue: Add system_dfl_long_wq for long unbound works")

Since the workqueue work doesn't rely on per-cpu variables, there is no
obvious reason that justify the use of a per-cpu workqueue. So change
system_long_wq with system_dfl_long_wq so that the work may benefit from
scheduler task placement.

Cc: MD Danish Anwar <danishanwar@ti.com>
Cc: Roger Quadros <rogerq@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
 drivers/net/ethernet/ti/icssg/icssg_stats.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ti/icssg/icssg_stats.c b/drivers/net/ethernet/ti/icssg/icssg_stats.c
index 7159baa0155c..7d6d6692d819 100644
--- a/drivers/net/ethernet/ti/icssg/icssg_stats.c
+++ b/drivers/net/ethernet/ti/icssg/icssg_stats.c
@@ -69,7 +69,7 @@ void icssg_stats_work_handler(struct work_struct *work)
 						stats_work.work);
 	emac_update_hardware_stats(emac);
 
-	queue_delayed_work(system_long_wq, &emac->stats_work,
+	queue_delayed_work(system_dfl_long_wq, &emac->stats_work,
 			   msecs_to_jiffies((STATS_TIME_LIMIT_1G_MS * 1000) / emac->speed));
 }
 EXPORT_SYMBOL_GPL(icssg_stats_work_handler);
-- 
2.54.0

Re: [RFC PATCH net-next 2/5] net: ti: icssg-stats: Move long delayed work on system_dfl_long_wq

[Richard Cheng]

On Mon, May 11, 2026 at 11:28:37AM +0800, Marco Crivellari wrote:
> Currently the code enqueue work items using {queue|mod}_delayed_work(),
> using system_long_wq. This workqueue should be used when long works are
> expected and it is a per-cpu workqueue.
> 
> The function(s) end up calling __queue_delayed_work(), which set a global
> timer that could fire anywhere, enqueuing the work where the timer fired.
> 
> Unbound works could benefit from scheduler task placement, to optimize
> performance and power consumption. Long work shouldn't stick to a single
> CPU.
> 
> Recently, a new unbound workqueue specific for long running work has
> been added:
> 
>     c116737e972e ("workqueue: Add system_dfl_long_wq for long unbound works")
> 
> Since the workqueue work doesn't rely on per-cpu variables, there is no
> obvious reason that justify the use of a per-cpu workqueue. So change
> system_long_wq with system_dfl_long_wq so that the work may benefit from
> scheduler task placement.
> 
> Cc: MD Danish Anwar <danishanwar@ti.com>
> Cc: Roger Quadros <rogerq@kernel.org>
> Cc: linux-arm-kernel@lists.infradead.org
> Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
> ---
>  drivers/net/ethernet/ti/icssg/icssg_stats.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/ti/icssg/icssg_stats.c b/drivers/net/ethernet/ti/icssg/icssg_stats.c
> index 7159baa0155c..7d6d6692d819 100644
> --- a/drivers/net/ethernet/ti/icssg/icssg_stats.c
> +++ b/drivers/net/ethernet/ti/icssg/icssg_stats.c
> @@ -69,7 +69,7 @@ void icssg_stats_work_handler(struct work_struct *work)
>  						stats_work.work);
>  	emac_update_hardware_stats(emac);
>  
> -	queue_delayed_work(system_long_wq, &emac->stats_work,
> +	queue_delayed_work(system_dfl_long_wq, &emac->stats_work,
>  			   msecs_to_jiffies((STATS_TIME_LIMIT_1G_MS * 1000) / emac->speed));
>  }
>  EXPORT_SYMBOL_GPL(icssg_stats_work_handler);
> -- 
> 2.54.0
> 
>

LGTM,
Reviewed-by: Richard Cheng <icheng@nvidia.com>

Best regards,
Richard Cheng. 

[RFC PATCH net-next 3/5] net: thunderbolt: Move long delayed work on system_dfl_long_wq

[Marco Crivellari]

Currently the code enqueue work items using {queue|mod}_delayed_work(),
using system_long_wq. This workqueue should be used when long works are
expected and it is a per-cpu workqueue.

The function(s) end up calling __queue_delayed_work(), which set a global
timer that could fire anywhere, enqueuing the work where the timer fired.

Unbound works could benefit from scheduler task placement, to optimize
performance and power consumption. Long work shouldn't stick to a single
CPU.

Recently, a new unbound workqueue specific for long running work has
been added:

    c116737e972e ("workqueue: Add system_dfl_long_wq for long unbound works")

Since the workqueue work doesn't rely on per-cpu variables, there is no
obvious reason that justify the use of a per-cpu workqueue. So change
system_long_wq with system_dfl_long_wq so that the work may benefit from
scheduler task placement.

Cc: Mika Westerberg <westeri@kernel.org>
Cc: Yehezkel Bernat <YehezkelShB@gmail.com>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
 drivers/net/thunderbolt/main.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/net/thunderbolt/main.c b/drivers/net/thunderbolt/main.c
index 7aae5d915a1e..f365ef642b62 100644
--- a/drivers/net/thunderbolt/main.c
+++ b/drivers/net/thunderbolt/main.c
@@ -315,7 +315,7 @@ static void start_login(struct tbnet *net)
 	net->login_received = false;
 	mutex_unlock(&net->connection_lock);
 
-	queue_delayed_work(system_long_wq, &net->login_work,
+	queue_delayed_work(system_dfl_long_wq, &net->login_work,
 			   msecs_to_jiffies(1000));
 }
 
@@ -464,7 +464,7 @@ static int tbnet_handle_packet(const void *buf, size_t size, void *data)
 			if (net->login_retries >= TBNET_LOGIN_RETRIES ||
 			    !net->login_sent) {
 				net->login_retries = 0;
-				queue_delayed_work(system_long_wq,
+				queue_delayed_work(system_dfl_long_wq,
 						   &net->login_work, 0);
 			}
 			mutex_unlock(&net->connection_lock);
@@ -704,7 +704,8 @@ static void tbnet_login_work(struct work_struct *work)
 		netdev_dbg(net->dev, "sending login request failed, ret=%d\n",
 			   ret);
 		if (net->login_retries++ < TBNET_LOGIN_RETRIES) {
-			queue_delayed_work(system_long_wq, &net->login_work,
+			queue_delayed_work(system_dfl_long_wq,
+					   &net->login_work,
 					   delay);
 		} else {
 			netdev_info(net->dev, "ThunderboltIP login timed out\n");
-- 
2.54.0

[RFC PATCH net-next 4/5] net: usb: pegasus: Move long delayed work on system_dfl_long_wq

[Marco Crivellari]

Currently the code enqueue work items using {queue|mod}_delayed_work(),
using system_long_wq. This workqueue should be used when long works are
expected and it is a per-cpu workqueue.

The function(s) end up calling __queue_delayed_work(), which set a global
timer that could fire anywhere, enqueuing the work where the timer fired.

Unbound works could benefit from scheduler task placement, to optimize
performance and power consumption. Long work shouldn't stick to a single
CPU.

Recently, a new unbound workqueue specific for long running work has
been added:

    c116737e972e ("workqueue: Add system_dfl_long_wq for long unbound works")

Since the workqueue work doesn't rely on per-cpu variables, there is no
obvious reason that justify the use of a per-cpu workqueue. So change
system_long_wq with system_dfl_long_wq so that the work may benefit from
scheduler task placement.

Cc: Petko Manolov <petkan@nucleusys.com>
Cc: linux-usb@vger.kernel.org
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
 drivers/net/usb/pegasus.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/net/usb/pegasus.c b/drivers/net/usb/pegasus.c
index db85f40734d7..f26bf54e606c 100644
--- a/drivers/net/usb/pegasus.c
+++ b/drivers/net/usb/pegasus.c
@@ -1126,8 +1126,9 @@ static void check_carrier(struct work_struct *work)
 	pegasus_t *pegasus = container_of(work, pegasus_t, carrier_check.work);
 	set_carrier(pegasus->net);
 	if (!(pegasus->flags & PEGASUS_UNPLUG)) {
-		queue_delayed_work(system_long_wq, &pegasus->carrier_check,
-			CARRIER_CHECK_DELAY);
+		queue_delayed_work(system_dfl_long_wq,
+				   &pegasus->carrier_check,
+				   CARRIER_CHECK_DELAY);
 	}
 }
 
@@ -1232,7 +1233,7 @@ static int pegasus_probe(struct usb_interface *intf,
 	res = register_netdev(net);
 	if (res)
 		goto out3;
-	queue_delayed_work(system_long_wq, &pegasus->carrier_check,
+	queue_delayed_work(system_dfl_long_wq, &pegasus->carrier_check,
 			   CARRIER_CHECK_DELAY);
 	dev_info(&intf->dev, "%s, %s, %pM\n", net->name,
 		 usb_dev_id[dev_index].name, net->dev_addr);
@@ -1297,7 +1298,7 @@ static int pegasus_resume(struct usb_interface *intf)
 		pegasus->intr_urb->actual_length = 0;
 		intr_callback(pegasus->intr_urb);
 	}
-	queue_delayed_work(system_long_wq, &pegasus->carrier_check,
+	queue_delayed_work(system_dfl_long_wq, &pegasus->carrier_check,
 				CARRIER_CHECK_DELAY);
 	return 0;
 }
-- 
2.54.0

[RFC PATCH net-next 5/5] r8152: Move long delayed work on system_dfl_long_wq

[Marco Crivellari]

Currently the code enqueue work items using {queue|mod}_delayed_work(),
using system_long_wq. This workqueue should be used when long works are
expected and it is a per-cpu workqueue.

The function(s) end up calling __queue_delayed_work(), which set a global
timer that could fire anywhere, enqueuing the work where the timer fired.

Unbound works could benefit from scheduler task placement, to optimize
performance and power consumption. Long work shouldn't stick to a single
CPU.

Recently, a new unbound workqueue specific for long running work has
been added:

    c116737e972e ("workqueue: Add system_dfl_long_wq for long unbound works")

Since the workqueue work doesn't rely on per-cpu variables, there is no
obvious reason that justify the use of a per-cpu workqueue. So change
system_long_wq with system_dfl_long_wq so that the work may benefit from
scheduler task placement.

Cc: Ethan Nelson-Moore <enelsonmoore@gmail.com>
Cc: linux-usb@vger.kernel.org
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
 drivers/net/usb/r8152.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 1ace1d2398c9..16c521e3fe0a 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -7050,7 +7050,8 @@ static void rtl_hw_phy_work_func_t(struct work_struct *work)
 
 		/* Delay execution in case request_firmware() is not ready yet.
 		 */
-		queue_delayed_work(system_long_wq, &tp->hw_phy_work, HZ * 10);
+		queue_delayed_work(system_dfl_long_wq, &tp->hw_phy_work,
+				   HZ * 10);
 		goto ignore_once;
 	}
 
@@ -8620,7 +8621,7 @@ static int rtl8152_reset_resume(struct usb_interface *intf)
 	clear_bit(SELECTIVE_SUSPEND, &tp->flags);
 	rtl_reset_ocp_base(tp);
 	tp->rtl_ops.init(tp);
-	queue_delayed_work(system_long_wq, &tp->hw_phy_work, 0);
+	queue_delayed_work(system_dfl_long_wq, &tp->hw_phy_work, 0);
 	set_ethernet_addr(tp, true);
 	return rtl8152_resume(intf);
 }
@@ -10001,7 +10002,7 @@ static int rtl8152_probe_once(struct usb_interface *intf,
 	/* Retry in case request_firmware() is not ready yet. */
 	tp->rtl_fw.retry = true;
 #endif
-	queue_delayed_work(system_long_wq, &tp->hw_phy_work, 0);
+	queue_delayed_work(system_dfl_long_wq, &tp->hw_phy_work, 0);
 	set_ethernet_addr(tp, false);
 
 	usb_set_intfdata(intf, tp);
-- 
2.54.0