From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f46.google.com (mail-oi0-f46.google.com [209.85.218.46]) by dpdk.org (Postfix) with ESMTP id 60D955930 for ; Thu, 24 Jul 2014 10:35:28 +0200 (CEST) Received: by mail-oi0-f46.google.com with SMTP id i138so1799167oig.19 for ; Thu, 24 Jul 2014 01:36:55 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=ygN2k+ehhMjyrHFbhKG0wlVkIoNk/E1KN+19T4plGfc=; b=Sv8M0HTxa780xsuUFk1hhRB1WNCKQ0es7gbWBZrladv76t5mlcTNKZkaNyH6ri1Y0+ BcQtvcGipG65RQgagnPoCYo+Uc58Fvp4f8zusRJ4wmzVxIExf0WiIqocxavg3GT24ZSD 2pY4iGyf60UQXKOUPAGhDSO3L6qVNfHLdeRQbfSuVJtK5rzTqAyh4tOyx2aobhFcZGxa JUwZUGeJUoDyeJ43GK+K9I/m289ZhVGlerVY4vRzoEyLCt7sIx2d9my6fDofd2kzn3fN YTjRSqgj8gS2EOTVdrZFrLLWcfxSyj8Ehz8jUCDn14f02M04W7OJA8KF0mjjUuQfM/Vu i2tQ== X-Gm-Message-State: ALoCoQmuZkEmwtdJEAxFR8v89ATSXcNHnUu7YmJbV0o1Q22b0F3ePnJkvoO3D4gUr+1XEfKtjAZb MIME-Version: 1.0 X-Received: by 10.182.66.79 with SMTP id d15mr10492978obt.49.1406191014901; Thu, 24 Jul 2014 01:36:54 -0700 (PDT) Received: by 10.202.55.198 with HTTP; Thu, 24 Jul 2014 01:36:54 -0700 (PDT) In-Reply-To: References: Date: Thu, 24 Jul 2014 11:36:54 +0300 Message-ID: From: Alex Markuze To: Kai Zhang Content-Type: text/plain; charset=UTF-8 Cc: "dev@dpdk.org" Subject: Re: [dpdk-dev] About round trip latency with DPDK X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 24 Jul 2014 08:35:28 -0000 Kai, the latency depends both on what you do and how much you send. A bigger packet will take longer time to transmit. Now that thats out of the way I propose you use perf to see how busy is the cpu and with what. FYI, ~10us is something that can be achieved with netperf with a kernel driver based on interrupts. The 0.7m latency indicates that something is wrong with your system. Basically make sure that the cpu is busy with polling only and a small percent handling the messages. Hope this helps somehow. On Wed, Jul 23, 2014 at 10:24 PM, Kai Zhang wrote: > Hello, > > I am trying to develop a low-latency application, and I measured the round > trip latency with DPDK. However I got an average of 650~720 microseconds > round-trip latency with Intel 82599 10Gbps NIC. > > The experiment method is as follows. 2 machines (A and B) are connected > back-to-back. Machine A embeds a time stamp in the packet and sends to B, B > (use testpmd or l2fwd) forwards packets back to A immediately (A->B->A), > and A receives packets and calculates time difference between current time > and the embedded time stamp. (code : > https://github.com/kay21s/dpdk/tree/master/examples/recv_send) > > I have 3 machines, and performing the above experiment on each pair leads > to a similar latency. However, previous academic papers report that DPDK > offers only a few 10 microseconds round trip latency. > > What's the round trip latency DPDK is supposed to offer? Have you measured > it at Intel? > > Thanks a lot, > Kai