From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: VMXNET3 on vmware, ping delay Date: Thu, 25 Jun 2015 22:20:44 +0300 Message-ID: <558C548C.4070602@cloudius-systems.com> References: <792CF0A6B0883C45AF8C719B2ECA946E42B2430F@DEMUMBX003.nsn-intra.net> <20150625151834.GA29296@mhcomputing.net> <558C2256.4070802@cloudius-systems.com> <1606901.Dh26nmAAAf@xps13> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: dev@dpdk.org To: Thomas Monjalon Return-path: Received: from mail-wi0-f173.google.com (mail-wi0-f173.google.com [209.85.212.173]) by dpdk.org (Postfix) with ESMTP id A8B0CC710 for ; Thu, 25 Jun 2015 21:20:46 +0200 (CEST) Received: by wicgi11 with SMTP id gi11so84966038wic.0 for ; Thu, 25 Jun 2015 12:20:46 -0700 (PDT) In-Reply-To: <1606901.Dh26nmAAAf@xps13> List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 06/25/2015 09:44 PM, Thomas Monjalon wrote: > 2015-06-25 18:46, Avi Kivity: >> On 06/25/2015 06:18 PM, Matthew Hall wrote: >>> On Thu, Jun 25, 2015 at 09:14:53AM +0000, Vass, Sandor (Nokia - HU/Budapest) wrote: >>>> According to my understanding each packet should go >>>> through BR as fast as possible, but it seems that the rte_eth_rx_burst >>>> retrieves packets only when there are at least 2 packets on the RX queue of >>>> the NIC. At least most of the times as there are cases (rarely - according >>>> to my console log) when it can retrieve 1 packet also and sometimes only 3 >>>> packets can be retrieved... >>> By default DPDK is optimized for throughput not latency. Try a test with >>> heavier traffic. >>> >>> There is also some work going on now for DPDK interrupt-driven mode, which >>> will work more like traditional Ethernet drivers instead of polling mode >>> Ethernet drivers. >>> >>> Though I'm not an expert on it, there is also a series of ways to optimize for >>> latency, which hopefully some others could discuss... or maybe search the >>> archives / web site / Intel tuning documentation. >>> >> What would be useful is a runtime switch between polling and interrupt >> modes. This was if the load is load you use interrupts, and as >> mitigation, you switch to poll mode, until the load drops again. > DPDK is not a stack. It's up to the DPDK application to poll or use interrupts > when needed. As long as DPDK provides a mechanism for a runtime switch, the application can do that.