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 37DD6CA5A; Mon, 29 Dec 2025 16:38:59 +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=1767026342; cv=none; b=gw4r8HHSLbIt6LtSq9pnyHkhz/5eMJKLl4WO83REaPpqBI6AofUrEud8l4+rhzp1u1RAMEyultsqR+Ukoo/qms4W1NBMTeV/dwTxDKPcOBph3p23fwxorlj2MSI+JVrHP6/yfvQIQLjDavI55NBvJ5Br6WxUDHBJ7RzhOnVyVd8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767026342; c=relaxed/simple; bh=GpifLfwkiu9eoC3V+KocP5lCF2mgL1SywA1OCMccwi8=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=btUJfmG0yhBrayQA3hDGiJLvEGq9Xvze3Yys/KTcba4nYaMJilIdqDYYvg/79NmxleYZU60aOeN0x0E6vIF6XtxcsdOnImatbKT0RZwxmn8oiJOVJFVgBxWTyvhbWd8yPoiJGt34RpgxB9WbhMo+nZWc1EPiKarF4X9JmnCrSGk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HLkNdk4h; 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="HLkNdk4h" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9B5B3C4CEF7; Mon, 29 Dec 2025 16:38:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767026339; bh=GpifLfwkiu9eoC3V+KocP5lCF2mgL1SywA1OCMccwi8=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=HLkNdk4hdwpfIXAI2Ox8hJv88WpG39J80SwhesPDoJ8n+Bzn38A0UaHPEnUuOMeVU BvWpV7oD+nueOW4XtOhACKEFN0CB5X2IQ9kpSGPrJSGJLhgrV2OHwlFEhhsgQBJRnN RSpc353okdJRve6qkaSCdQC8AQouDVQ/5FHMdvQ9dWGnzY7hjxDfq4BTxCRGeSyOFU uefrw/XXHOYS++YnbEK0t6qyqtfM6vWkI/sJ/VYuPA+aStojG6sWrdmHvOs4a14SjF +nUh2sdJbwKuRKX2QXYtz6rZzlBNGXC3VDf/nguI5vBfyVxxZQE7Q9SNd8kp4/SLz0 MQXpxA7/s5ywg== Date: Mon, 29 Dec 2025 10:38:58 -0600 From: Bjorn Helgaas To: Marco Crivellari Cc: linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Tejun Heo , Lai Jiangshan , Frederic Weisbecker , Sebastian Andrzej Siewior , Michal Hocko , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Bjorn Helgaas Subject: Re: [PATCH] PCI: pnv_php: add WQ_PERCPU to alloc_workqueue users Message-ID: <20251229163858.GA63361@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: <20251107143335.242342-1-marco.crivellari@suse.com> On Fri, Nov 07, 2025 at 03:33:35PM +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. Thanks for these patches. We have: [PATCH] PCI: endpoint: add WQ_PERCPU to alloc_workqueue users [PATCH] PCI: endpoint: epf-mhi: add WQ_PERCPU to alloc_workqueue users [PATCH] PCI: endpoint: pci-epf-test: add WQ_PERCPU to alloc_workqueue users [PATCH] PCI: pnv_php: add WQ_PERCPU to alloc_workqueue users [PATCH] PCI: shpchp: add WQ_PERCPU to alloc_workqueue users [PATCH] PCI: endpoint: replace use of system_wq with system_percpu_wq IIUC these are all part of the same effort to refactor the workqueue API and don't really have anything to do with the endpoint or hotplug drivers themselves. So I put these all on pci/workqueue and squashed the WQ_PERCPU patches together because they do the same thing, they have the same commit log, and there's not really any point in reviewing them separately. > Suggested-by: Tejun Heo > Signed-off-by: Marco Crivellari > --- > drivers/pci/hotplug/pnv_php.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/pci/hotplug/pnv_php.c b/drivers/pci/hotplug/pnv_php.c > index c5345bff9a55..35f1758126c6 100644 > --- a/drivers/pci/hotplug/pnv_php.c > +++ b/drivers/pci/hotplug/pnv_php.c > @@ -802,7 +802,7 @@ static struct pnv_php_slot *pnv_php_alloc_slot(struct device_node *dn) > } > > /* Allocate workqueue for this slot's interrupt handling */ > - php_slot->wq = alloc_workqueue("pciehp-%s", 0, 0, php_slot->name); > + php_slot->wq = alloc_workqueue("pciehp-%s", WQ_PERCPU, 0, php_slot->name); > if (!php_slot->wq) { > SLOT_WARN(php_slot, "Cannot alloc workqueue\n"); > kfree(php_slot->name); > -- > 2.51.1 >