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[109.64.91.49]) by smtp.gmail.com with ESMTPSA id l13sm41378138wrm.24.2020.11.19.06.46.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Nov 2020 06:46:31 -0800 (PST) Date: Thu, 19 Nov 2020 09:46:26 -0500 From: "Michael S. Tsirkin" To: Stefan Hajnoczi Subject: Re: [PATCH 00/10] vhost/qemu: thread per IO SCSI vq Message-ID: <20201119094315-mutt-send-email-mst@kernel.org> References: <1605223150-10888-1-git-send-email-michael.christie@oracle.com> <20201117164043.GS131917@stefanha-x1.localdomain> <20201118113117.GF182763@stefanha-x1.localdomain> MIME-Version: 1.0 In-Reply-To: <20201118113117.GF182763@stefanha-x1.localdomain> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/19 03:44:58 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: fam@euphon.net, linux-scsi@vger.kernel.org, jasowang@redhat.com, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, target-devel@vger.kernel.org, pbonzini@redhat.com, Mike Christie Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Nov 18, 2020 at 11:31:17AM +0000, Stefan Hajnoczi wrote: > > My preference has been: > > > > 1. If we were to ditch cgroups, then add a new interface that would allow > > us to bind threads to a specific CPU, so that it lines up with the guest's > > mq to CPU mapping. > > A 1:1 vCPU/vq->CPU mapping isn't desirable in all cases. > > The CPU affinity is a userspace policy decision. The host kernel should > provide a mechanism but not the policy. That way userspace can decide > which workers are shared by multiple vqs and on which physical CPUs they > should run. So if we let userspace dictate the threading policy then I think binding vqs to userspace threads and running there makes the most sense, no need to create the threads. -- MST