[RFC PATCH net-next] net: macb: Move delayed work on system_dfl_wq

[RFC PATCH net-next] net: macb: Move delayed work on system_dfl_wq

[Marco Crivellari]

Currently the code enqueue work items using {queue|mod}_delayed_work(),
using system_wq, which will be deprecated soon and replaced by
system_percpu_wq.

   commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq")

The function(s) mentioned earlier, 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.

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_wq with system_dfl_wq so that the work may benefit from
scheduler task placement.

Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
 drivers/net/ethernet/cadence/macb_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index a12aa21244e8..42328b5ca403 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -672,7 +672,7 @@ static void macb_tx_lpi_work_fn(struct work_struct *work)
 static void macb_tx_lpi_schedule(struct macb *bp)
 {
 	if (bp->eee_active)
-		mod_delayed_work(system_wq, &bp->tx_lpi_work,
+		mod_delayed_work(system_dfl_wq, &bp->tx_lpi_work,
 				 usecs_to_jiffies(bp->tx_lpi_timer));
 }
 
@@ -724,7 +724,7 @@ static int macb_mac_enable_tx_lpi(struct phylink_config *config, u32 timer,
 	/* Defer initial LPI entry by 1 second after link-up per
 	 * IEEE 802.3az section 22.7a.
 	 */
-	mod_delayed_work(system_wq, &bp->tx_lpi_work, msecs_to_jiffies(1000));
+	mod_delayed_work(system_dfl_wq, &bp->tx_lpi_work, msecs_to_jiffies(1000));
 
 	return 0;
 }
-- 
2.54.0

Re: [RFC PATCH net-next] net: macb: Move delayed work on system_dfl_wq

[Nicolai Buchwitz]

On 15.5.2026 17:27, Marco Crivellari wrote:
> Currently the code enqueue work items using {queue|mod}_delayed_work(),
> using system_wq, which will be deprecated soon and replaced by
> system_percpu_wq.
> 
>    commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and 
> system_dfl_wq")
> 
> The function(s) mentioned earlier, 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.
> 
> 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_wq with system_dfl_wq so that the work may benefit from
> scheduler task placement.
> 
> Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
> ---
>  drivers/net/ethernet/cadence/macb_main.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cadence/macb_main.c 
> b/drivers/net/ethernet/cadence/macb_main.c
> index a12aa21244e8..42328b5ca403 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -672,7 +672,7 @@ static void macb_tx_lpi_work_fn(struct work_struct 
> *work)
>  static void macb_tx_lpi_schedule(struct macb *bp)
>  {
>  	if (bp->eee_active)
> -		mod_delayed_work(system_wq, &bp->tx_lpi_work,
> +		mod_delayed_work(system_dfl_wq, &bp->tx_lpi_work,
>  				 usecs_to_jiffies(bp->tx_lpi_timer));
>  }
> 
> @@ -724,7 +724,7 @@ static int macb_mac_enable_tx_lpi(struct 
> phylink_config *config, u32 timer,
>  	/* Defer initial LPI entry by 1 second after link-up per
>  	 * IEEE 802.3az section 22.7a.
>  	 */
> -	mod_delayed_work(system_wq, &bp->tx_lpi_work, 
> msecs_to_jiffies(1000));
> +	mod_delayed_work(system_dfl_wq, &bp->tx_lpi_work, 
> msecs_to_jiffies(1000));
> 
>  	return 0;
>  }

Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>

Thanks
Nicolai