From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6AEDC3A1E66; Mon, 29 Dec 2025 16:41:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767026461; cv=none; b=MN8KW5aPKxVRShIKw+FBhw5yzKXXjjOSnGmxfsauJlGCP4ltHdS08ZFsNSc1kIiuNAtCD7vMZDgbpk0X+7SlVPi2CiKf6AYx4a41AD5Cb8ermks8HEoLaiTUhfrIAq691KtsDXTL07/SaXEcmE/o80aZOncWZRDPO5b0wmB0UeA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767026461; c=relaxed/simple; bh=TCOm2rpJ9OfMmoFF8qLCjdeSTuH9rwbAp36mqtKXFwQ=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=hZFUcRHgdt/WmCSBLR+fBonu6HrJT9ZA4VYVux4c8u32WhkBmFoUgNVdXBJqUjgZx1CZh/YZSX8ci0wevgoq8VSAsFkimY+RWNUMfoVNfWoRwcFAyNHJeZeUBBANR3hGgIgjBqOfQzQBZ06ZrIpUtLBmIO7RucTNUgIeH+ZurQw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=SCrOUkxD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="SCrOUkxD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0601BC4CEF7; Mon, 29 Dec 2025 16:41:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767026461; bh=TCOm2rpJ9OfMmoFF8qLCjdeSTuH9rwbAp36mqtKXFwQ=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=SCrOUkxD/fqe0Uj8Z+gIaxo/OAcM/I9RZS+8x8Vu+ElHvSFcWZmxRskuec642feIa 5LxlBqlU/HOd0Rd+36uLnThkwZOJJmgB69EAL6ZDXCEfOGcNccFO0QQEc4E4mLEuis S+QKquV301HMvyIhtfeoc/NzhcvkozHh46JJWZE/QpjfwGji5/0Ktbt+oitQ7IcgQr fsSSWipTaUZBwkCHwUg9Dx5XUcTOIOZkmk2W6AjtQzBUZVqHhCTRTMhFB9F20mSpvq 8nixt/vMYZTrZ+7tupsy2yVsYaGSlpmW1DUOQV6xXcN7Umw43vktAdOauB1dCA2whX jMoyrB/lCVr8w== Date: Mon, 29 Dec 2025 10:40:59 -0600 From: Bjorn Helgaas To: Marco Crivellari Cc: linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, Tejun Heo , Lai Jiangshan , Frederic Weisbecker , Sebastian Andrzej Siewior , Michal Hocko , Bjorn Helgaas , Ilpo Jarvinen , Manivannan Sadhasivam Subject: Re: [PATCH] PCI: shpchp: add WQ_PERCPU to alloc_workqueue users Message-ID: <20251229164059.GA65997@bhelgaas> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20251107143624.244978-1-marco.crivellari@suse.com> [+cc Mani] On Fri, Nov 07, 2025 at 03:36:24PM +0100, Marco Crivellari wrote: > Currently if a user enqueues a work item using schedule_delayed_work() the > used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use > WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to > schedule_work() that is using system_wq and queue_work(), that makes use > again of WORK_CPU_UNBOUND. > This lack of consistency cannot be addressed without refactoring the API. > > alloc_workqueue() treats all queues as per-CPU by default, while unbound > workqueues must opt-in via WQ_UNBOUND. > > This default is suboptimal: most workloads benefit from unbound queues, > allowing the scheduler to place worker threads where they’re needed and > reducing noise when CPUs are isolated. > > This continues the effort to refactor workqueue APIs, which began with > the introduction of new workqueues and a new alloc_workqueue flag in: > > commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq") > commit 930c2ea566af ("workqueue: Add new WQ_PERCPU flag") > > This change adds a new WQ_PERCPU flag to explicitly request > alloc_workqueue() to be per-cpu when WQ_UNBOUND has not been specified. > > With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND), > any alloc_workqueue() caller that doesn’t explicitly specify WQ_UNBOUND > must now use WQ_PERCPU. > > Once migration is complete, WQ_UNBOUND can be removed and unbound will > become the implicit default. > > Suggested-by: Tejun Heo > Signed-off-by: Marco Crivellari Squashed with similar patches [1] and applied on pci/workqueue for v6.20, thanks! See https://lore.kernel.org/r/20251229163858.GA63361@bhelgaas > --- > drivers/pci/hotplug/shpchp_core.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/hotplug/shpchp_core.c b/drivers/pci/hotplug/shpchp_core.c > index 0c341453afc6..56308515ecba 100644 > --- a/drivers/pci/hotplug/shpchp_core.c > +++ b/drivers/pci/hotplug/shpchp_core.c > @@ -80,7 +80,8 @@ static int init_slots(struct controller *ctrl) > slot->device = ctrl->slot_device_offset + i; > slot->number = ctrl->first_slot + (ctrl->slot_num_inc * i); > > - slot->wq = alloc_workqueue("shpchp-%d", 0, 0, slot->number); > + slot->wq = alloc_workqueue("shpchp-%d", WQ_PERCPU, 0, > + slot->number); > if (!slot->wq) { > retval = -ENOMEM; > goto error_slot; > -- > 2.51.1 >