From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030634AbXBGPty (ORCPT ); Wed, 7 Feb 2007 10:49:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030637AbXBGPty (ORCPT ); Wed, 7 Feb 2007 10:49:54 -0500 Received: from wx-out-0506.google.com ([66.249.82.227]:62654 "EHLO wx-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030634AbXBGPty (ORCPT ); Wed, 7 Feb 2007 10:49:54 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=cyuI2Ru4a6heUJ9zWSFLiDlFZg4DnFmXkCJpldw0fc/sRR6HjBegCdSTpp0phKRWDttncsTxez6GctOzHgvqGeFnkzWurcvqbdpdSR0aQ3sM3GGsiXJFr3dl9y7XMC5zygAf5m+HfmKrYP5rFrMAkuQUpunTace4t10aQGrxqjo= Message-ID: Date: Wed, 7 Feb 2007 10:49:53 -0500 From: "Sen Horak" To: lkml Subject: Performance of concurrent senders In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline References: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi -- I have been running some experiments involving processes sending large volumes of data concurrently. The results show (on Linux 2.6.19.2) that although the total throughput achieved by all the processes remains constant, the jitter increases as the number of processes increases. Beyond about 64 processes (on a 2.4GHz Xeon with 4Mb of cache), processes start getting starved and the streams get very bursty. Are there any steps one can take to make the jitter scale better, eg. by using another scheduler? I guess that it is reasonable that the jitter grow with added contention through the TCP/IP stack - but what growth rate is acceptable? Is the data I have below reasonable? The jitter varies as follows and is shown as an average+/- sd across 25 10-second intervals. Concurrency Jitter (us) 1 1.6+/-0.8 2 1.5+/-1.1 4 1.4+/-0.6 8 0.8+/-0.5 12 2.3+/-1.2 16 3.3+/-2.1 20 4.6+/-2.5 24 6.2+/-1.4 28 7.8+/-3.2 32 10.0+/-3.4 64 100+ Sen