From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH V2 6/6] vhost_net: correctly limit the max pending buffers Date: Mon, 02 Sep 2013 16:37:38 +0800 Message-ID: <52244E52.3060408@redhat.com> References: <1377836962-49780-1-git-send-email-jasowang@redhat.com> <1377836962-49780-7-git-send-email-jasowang@redhat.com> <20130902055609.GC19838@redhat.com> <52243071.5090303@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <52243071.5090303@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: "Michael S. Tsirkin" Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org On 09/02/2013 02:30 PM, Jason Wang wrote: > On 09/02/2013 01:56 PM, Michael S. Tsirkin wrote: >> > On Fri, Aug 30, 2013 at 12:29:22PM +0800, Jason Wang wrote: >>> >> As Michael point out, We used to limit the max pending DMAs to get better cache >>> >> utilization. But it was not done correctly since it was one done when there's no >>> >> new buffers submitted from guest. Guest can easily exceeds the limitation by >>> >> keeping sending packets. >>> >> >>> >> So this patch moves the check into main loop. Tests shows about 5%-10% >>> >> improvement on per cpu throughput for guest tx. But a 5% drop on per cpu >>> >> transaction rate for a single session TCP_RR. >> > Any explanation for the drop? single session TCP_RR is unlikely to >> > exceed VHOST_MAX_PEND, correct? > Unlikely to exceed. Recheck the result, looks like it was not stable > enough. Will re-test and report. Re-tested with more iterations, result shows no difference on TCP_RR test and 5%-10% improvement on per cpu throughput for guest tx. Will post V3 soon.