From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH] vhost: Add polling mode Date: Sun, 17 Aug 2014 14:58:09 +0200 Message-ID: <20140817125809.GA22213@redhat.com> References: <1407659404-razya@il.ibm.com> <20140810083035.0CF58380729@moren.haifa.ibm.com> <20140810194559.GA4344@redhat.com> <20140811.124621.576073630604147753.davem@davemloft.net> <20140812091850.GD6440@redhat.com> <20140813121550.GA21026@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Eran Raichstein , kvm-owner@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, abel.gordon@gmail.com, Alex Glikson , Yossi Kuperman1 , Joel Nider , netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, David Miller To: Razya Ladelsky Return-path: Content-Disposition: inline In-Reply-To: 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 List-Id: netdev.vger.kernel.org On Sun, Aug 17, 2014 at 03:35:39PM +0300, Razya Ladelsky wrote: > > > > > > Hi Michael, > > > > > > Sorry for the delay, had some problems with my mailbox, and I realized > > > > just now that > > > my reply wasn't sent. > > > The vm indeed ALWAYS utilized 100% cpu, whether polling was enabled or > > > > not. > > > The vhost thread utilized less than 100% (of the other cpu) when > polling > > > was disabled. > > > Enabling polling increased its utilization to 100% (in which case both > > > > cpus were 100% utilized). > > > > Hmm this means the testing wasn't successful then, as you said: > > > > The idea was to get it 100% loaded, so we can see that the polling is > > getting it to produce higher throughput. > > > > in fact here you are producing more throughput but spending more power > > to produce it, which can have any number of explanations besides polling > > improving the efficiency. For example, increasing system load might > > disable host power management. > > > > Hi Michael, > I re-ran the tests, this time with the "turbo mode" and "C-states" > features off. > No Polling: > 1 VM running netperf (msg size 64B): 1107 Mbits/sec > Polling: > 1 VM running netperf (msg size 64B): 1572 Mbits/sec > > > > > > > > As you can see from the new results, the numbers are lower, > but relatively (polling on/off) there's no change. > Thank you, > Razya That was just one example. There many other possibilities. Either actually make the systems load all host CPUs equally, or divide throughput by host CPU. > > > > > > > > > > > -- > > > > MST > > > > > > -- > > To unsubscribe from this list: send the line "unsubscribe kvm" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > >