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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , "Christophe Leroy (CS GROUP)" , Ethan Nelson-Moore , Haren Myneni , Madhavan Srinivasan , MD Danish Anwar , Michael Ellerman , Mika Westerberg , Nicholas Piggin , Nick Child , Petko Manolov , Rick Lindsley , Roger Quadros , Yehezkel Bernat Subject: [RFC PATCH net-next 0/5] net: Move system_long_wq to system_dfl_long_wq Date: Mon, 11 May 2026 11:28:35 +0200 Message-ID: <20260511092846.120141-1-marco.crivellari@suse.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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