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Fri, 08 May 2026 06:45:51 -0700 (PDT) Received: from localhost.localdomain ([2a00:6d43:105:c401:e307:1a37:2e76:ce91]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48e6db1413csm178475e9.29.2026.05.08.06.45.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 May 2026 06:45:50 -0700 (PDT) From: Marco Crivellari To: linux-kernel@vger.kernel.org Cc: Tejun Heo , Lai Jiangshan , Frederic Weisbecker , Sebastian Andrzej Siewior , Marco Crivellari , Michal Hocko , Al Viro , David Sterba , David Woodhouse , Eric Sandeen , John Paul Adrian Glaubitz , Kees Cook , Miklos Szeredi , Richard Weinberger , Viacheslav Dubeyko , Yangtao Li Subject: [RFC PATCH 0/6] fs: Move long delayed work on system_dfl_long_wq Date: Fri, 8 May 2026 15:45:28 +0200 Message-ID: <20260508134541.282073-1-marco.crivellari@suse.com> X-Mailer: git-send-email 2.53.0 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 (6): ufs: Move long delayed work on system_dfl_long_wq fs/jffs2: Move long delayed work on system_dfl_long_wq hfsplus: Move long delayed work on system_dfl_long_wq hfs: Move long delayed work on system_dfl_long_wq fuse: dax: Move long delayed work on system_dfl_long_wq affs: Move long delayed work on system_dfl_long_wq fs/affs/super.c | 2 +- fs/fuse/dax.c | 2 +- fs/hfs/super.c | 2 +- fs/hfsplus/super.c | 2 +- fs/jffs2/wbuf.c | 2 +- fs/ufs/super.c | 2 +- 6 files changed, 6 insertions(+), 6 deletions(-) -- 2.53.0