From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935204AbcHaOZB (ORCPT ); Wed, 31 Aug 2016 10:25:01 -0400 Received: from mail-yw0-f196.google.com ([209.85.161.196]:35874 "EHLO mail-yw0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935089AbcHaOY6 (ORCPT ); Wed, 31 Aug 2016 10:24:58 -0400 Date: Wed, 31 Aug 2016 10:24:56 -0400 From: Tejun Heo To: Bhaktipriya Shridhar Cc: Christoffer Dall , Marc Zyngier , Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] KVM: Remove deprecated create_singlethread_workqueue Message-ID: <20160831142456.GL12660@htj.duckdns.org> References: <20160830175950.GA5958@Karyakshetra> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160830175950.GA5958@Karyakshetra> User-Agent: Mutt/1.7.0 (2016-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 30, 2016 at 11:29:51PM +0530, Bhaktipriya Shridhar wrote: > The workqueue "irqfd_cleanup_wq" queues a single work item > &irqfd->shutdown and hence doesn't require ordering. It is a host-wide > workqueue for issuing deferred shutdown requests aggregated from all > vm* instances. It is not being used on a memory reclaim path. > Hence, it has been converted to use system_wq. > The work item has been flushed in kvm_irqfd_release(). > > The workqueue "wqueue" queues a single work item &timer->expired > and hence doesn't require ordering. Also, it is not being used on > a memory reclaim path. Hence, it has been converted to use system_wq. > > System workqueues have been able to handle high level of concurrency > for a long time now and hence it's not required to have a singlethreaded > workqueue just to gain concurrency. Unlike a dedicated per-cpu workqueue > created with create_singlethread_workqueue(), system_wq allows multiple > work items to overlap executions even on the same CPU; however, a > per-cpu workqueue doesn't have any CPU locality or global ordering > guarantee unless the target CPU is explicitly specified and thus the > increase of local concurrency shouldn't make any difference. > > Signed-off-by: Bhaktipriya Shridhar Acked-by: Tejun Heo Thanks. -- tejun