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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 Cc: Mike Christie , qemu-devel@nongnu.org, fam@euphon.net, linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, jasowang@redhat.com, pbonzini@redhat.com, virtualization@lists.linux-foundation.org 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 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201118113117.GF182763@stefanha-x1.localdomain> Precedence: bulk List-ID: X-Mailing-List: target-devel@vger.kernel.org Archived-At: List-Archive: List-Post: 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