[PATCH net-next v4 1/6] ibmvnic: Move long delayed work on system_dfl_long_wq

[PATCH net-next v4 1/6] 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 | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 5a510eed335e..d4c284c8ef43 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 {
@@ -3454,7 +3454,7 @@ static int ibmvnic_reset(struct ibmvnic_adapter *adapter,
 	list_add_tail(&rwi->list, &adapter->rwi_list);
 	netdev_dbg(adapter->netdev, "Scheduling reset (reason %s)\n",
 		   reset_reason_to_string(reason));
-	queue_work(system_long_wq, &adapter->ibmvnic_reset);
+	queue_work(system_dfl_long_wq, &adapter->ibmvnic_reset);
 
 	ret = 0;
 err:
-- 
2.55.0

Re: [PATCH net-next v4 1/6] ibmvnic: Move long delayed work on system_dfl_long_wq

[mingming cao]

On 10/12/26 2:54 AM, 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: 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 | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
> index 5a510eed335e..d4c284c8ef43 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 {
> @@ -3454,7 +3454,7 @@ static int ibmvnic_reset(struct ibmvnic_adapter *adapter,
>   	list_add_tail(&rwi->list, &adapter->rwi_list);
>   	netdev_dbg(adapter->netdev, "Scheduling reset (reason %s)\n",
>   		   reset_reason_to_string(reason));
> -	queue_work(system_long_wq, &adapter->ibmvnic_reset);
> +	queue_work(system_dfl_long_wq, &adapter->ibmvnic_reset);
>   
>   	ret = 0;
>   err:
On 10/12/26 2:54 AM, 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: 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 | 6 +++---
 >   1 file changed, 3 insertions(+), 3 deletions(-)
 >
 > diff --git a/drivers/net/ethernet/ibm/ibmvnic.c 
b/drivers/net/ethernet/ibm/ibmvnic.c
 > index 5a510eed335e..d4c284c8ef43 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 {
 > @@ -3454,7 +3454,7 @@ static int ibmvnic_reset(struct ibmvnic_adapter 
*adapter,
 >   	list_add_tail(&rwi->list, &adapter->rwi_list);
 >   	netdev_dbg(adapter->netdev, "Scheduling reset (reason %s)\n",
 >   		   reset_reason_to_string(reason));
 > -	queue_work(system_long_wq, &adapter->ibmvnic_reset);
 > +	queue_work(system_dfl_long_wq, &adapter->ibmvnic_reset);
 >
 >   	ret = 0;
 >   err:
I walked through the reset path and the conversion looks fine.

All three system_long_wq users move together and there are no
remaining users in the driver. The work items don't rely on per-CPU
state, so system_dfl_long_wq seems appropriate here.

Minor commit message nit: ibmvnic doesn't use mod_delayed_work(), and
one of the conversions is queue_work() rather than delayed work.

Acked-by: Mingming Cao <mmc@linux.ibm.com>

Re: [PATCH net-next v4 1/6] ibmvnic: Move long delayed work on system_dfl_long_wq

[Marco Crivellari]

On Fri, Oct 16, 2026 at 11:20 PM mingming cao <mmc@linux.ibm.com> wrote:
> [...]
> I walked through the reset path and the conversion looks fine.
>
> All three system_long_wq users move together and there are no
> remaining users in the driver. The work items don't rely on per-CPU
> state, so system_dfl_long_wq seems appropriate here.
>
> Minor commit message nit: ibmvnic doesn't use mod_delayed_work(), and
> one of the conversions is queue_work() rather than delayed work.
>
> Acked-by: Mingming Cao <mmc@linux.ibm.com>

Thanks for your comment.

drivers/net/ethernet/ibm/ibmvnic.c uses queue_delayed_work() and as
you mentioned one queue_work(). The workqueue used here was also
migrated based on Sashiko's feedback received in v2:

https://lore.kernel.org/all/20260711164434.1691221-3-horms@kernel.org/

I will keep your Ack for this patch in v5.

Thanks!

-- 

Marco Crivellari

SUSE Labs