From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <chrispappas12@gmail.com>
Received: from mail-oa0-f50.google.com (mail-oa0-f50.google.com
 [209.85.219.50]) by dpdk.org (Postfix) with ESMTP id A21C8595A
 for <dev@dpdk.org>; Mon, 21 Jul 2014 21:24:02 +0200 (CEST)
Received: by mail-oa0-f50.google.com with SMTP id g18so8133146oah.23
 for <dev@dpdk.org>; Mon, 21 Jul 2014 12:25:17 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113;
 h=mime-version:from:date:message-id:subject:to:content-type;
 bh=TRf9CHpHl2slMnjWlp0LeTv/jlufo8/J6dnd8pYqVS4=;
 b=pSJuVCbB6ls9lshOL6UYuYdfjm4S4RhGcXwKneZ/eVRe0OGKT6jcxgXPwbbV5Zo3xh
 a4vmWXfC+OOaf1OenyAutIh8AO83G58INWUQFHnEaDWVgix9UmW9V2lkZukVMgHm1At1
 gQNFbsxlaqQuvxr67qwa51lNW9VTmznO/h1jYz2rNdXEa51GMWIPlqfcLKKhzcKmP93Z
 eiWleurQ9aEplEV1g6D5ckMyHX0XqXUIByKJJUrXzY2KU7u7zdTG+dFQbsAnmOrXp3q+
 uLF/bFCHws/tgD/FKhfbYNPUWAAJIucNJWvWiqUgne2gkxlO6mHM0Zo0iBE6HhSXK97P
 yHQA==
X-Received: by 10.60.161.136 with SMTP id xs8mr40729812oeb.42.1405970717147;
 Mon, 21 Jul 2014 12:25:17 -0700 (PDT)
MIME-Version: 1.0
Received: by 10.76.86.72 with HTTP; Mon, 21 Jul 2014 12:24:36 -0700 (PDT)
From: Chris Pappas <chrispappas12@gmail.com>
Date: Mon, 21 Jul 2014 21:24:36 +0200
Message-ID: <CAE4G5iryAeKytnVLvpFoL7CmrnXxo_Gw0cmwOaAzNvvagr3QEg@mail.gmail.com>
To: dev@dpdk.org
Content-Type: text/plain; charset=UTF-8
X-Content-Filtered-By: Mailman/MimeDel 2.1.15
Subject: [dpdk-dev] Random numbers at line-rate
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: Mon, 21 Jul 2014 19:24:03 -0000

Hi,

I need to generate a random number per packet and I used the rte_fast_rand
function to do so. When I run the code for one port-core I get almost
line-rate performance. However, running simultaneously on multiple cores
degrades performance significantly. (in all cases I uses minimum-sized
packets).

Shouldn't the implementation scale for multicore and not degrade
performance or am I missing anything? Also, is there another recommendation
for generating randomness at line-rate? (the cpu does not support rdrand).

Best regards,
Chris