From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <junhanece@gmail.com>
Received: from mail-ob0-f169.google.com (mail-ob0-f169.google.com
 [209.85.214.169]) by dpdk.org (Postfix) with ESMTP id 541E668A1
 for <dev@dpdk.org>; Thu, 22 May 2014 18:43:51 +0200 (CEST)
Received: by mail-ob0-f169.google.com with SMTP id vb8so4126226obc.28
 for <dev@dpdk.org>; Thu, 22 May 2014 09:44:00 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113;
 h=mime-version:date:message-id:subject:from:to:content-type;
 bh=vQd7gsZCs2cKG2pCcpgnNYnvwyjuSGXgcrqXe4E1XkI=;
 b=qoiDsq9VoxBqfmZbE1jStI+5ydGBwVubxXl8qlW8obaT/7g2kVS8grJUJ2J2gL78jN
 telinEp63GPhHDsGlOGAqNNWlaoqag5LFOZVKzIVJXqavFuEh6EnijxOCcLR0LEa6asV
 71nnGje6jdc/INY1x0Pp92ViZQrlP7yBcHxLZkJgtYLmiTaZE6YWK6/TL/XvKLUiFvkk
 cQrsTh6+HPjg6SFJDbSrQqMTaDGqZdBptWAh/lXGazHjwv0X0HREgg4+3tw3+rS8C3PX
 okLFpe8r4eYBiLOceutzPJNhzHHP3veQ8cJpE0LJ/nnp4CWnmzqR7JU6lnKHrUXo7hS6
 oHug==
MIME-Version: 1.0
X-Received: by 10.60.149.233 with SMTP id ud9mr32933282oeb.66.1400777040807;
 Thu, 22 May 2014 09:44:00 -0700 (PDT)
Received: by 10.76.76.72 with HTTP; Thu, 22 May 2014 09:44:00 -0700 (PDT)
Date: Thu, 22 May 2014 18:44:00 +0200
Message-ID: <CAGeT4P+2shS+goNQbs1MH0ye+8OdndAG-J6qb3Gjkeht+XKH7Q@mail.gmail.com>
From: Jun Han <junhanece@gmail.com>
To: "dev@dpdk.org" <dev@dpdk.org>
Content-Type: text/plain; charset=UTF-8
X-Content-Filtered-By: Mailman/MimeDel 2.1.15
Subject: [dpdk-dev] DPDK Latency Issue
X-BeenThere: dev@dpdk.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: patches and discussions about DPDK <dev.dpdk.org>
List-Unsubscribe: <http://dpdk.org/ml/options/dev>,
 <mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://dpdk.org/ml/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <http://dpdk.org/ml/listinfo/dev>,
 <mailto:dev-request@dpdk.org?subject=subscribe>
X-List-Received-Date: Thu, 22 May 2014 16:43:51 -0000

Hi all,

I measured a roundtrip latency (using Spirent traffic generator) of sending
64B packets over a 10GbE to DPDK, and DPDK does nothing but simply forward
back to the incoming port (l3fwd without any lookup code, i.e., dstport =
port_id).

However, to my surprise, the average latency was around 150 usec. (The
packet drop rate was only 0.001%, i.e., 283 packets/sec dropped) Another
test I did was to measure the latency due to sending only a single 64B
packet, and the latency I measured is ranging anywhere from 40 usec to 100
usec.

I do not understand why this is so slow. Can someone explain the reasoning
behind this phenomenon?

Thank you so much!