From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3EAABC282CE for ; Tue, 4 Jun 2019 07:24:30 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 16C0324AEC for ; Tue, 4 Jun 2019 07:24:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 16C0324AEC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([127.0.0.1]:47244 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hY3o5-00067e-AE for qemu-devel@archiver.kernel.org; Tue, 04 Jun 2019 03:24:29 -0400 Received: from eggs.gnu.org ([209.51.188.92]:41200) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hY3ig-00027f-2Z for qemu-devel@nongnu.org; Tue, 04 Jun 2019 03:18:55 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hY3av-0000Kq-Gj for qemu-devel@nongnu.org; Tue, 04 Jun 2019 03:10:54 -0400 Received: from mga06.intel.com ([134.134.136.31]:34984) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hY3au-0008TL-FE for qemu-devel@nongnu.org; Tue, 04 Jun 2019 03:10:53 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Jun 2019 00:10:46 -0700 Received: from likexu-mobl1.ccr.corp.intel.com (HELO [10.239.196.173]) ([10.239.196.173]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/AES256-SHA; 04 Jun 2019 00:10:45 -0700 To: "Michael S. Tsirkin (level 24/vhost) (qemu.patchwork.ozlabs)" From: Like Xu Organization: Intel OTC Message-ID: <449c062f-373c-b310-ccc6-f14c702c8f19@linux.intel.com> Date: Tue, 4 Jun 2019 15:10:43 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 134.134.136.31 Subject: [Qemu-devel] [QUESTION] How to reduce network latency to improve netperf TCP_RR drastically? X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "qemu-devel@nongnu.org Developers" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Michael， At https://www.linux-kvm.org/page/NetworkingTodo, there is an entry for network latency saying: --- reduce networking latency: allow handling short packets from softirq or VCPU context Plan: We are going through the scheduler 3 times (could be up to 5 if softirqd is involved) Consider RX: host irq -> io thread -> VCPU thread -> guest irq -> guest thread. This adds a lot of latency. We can cut it by some 1.5x if we do a bit of work either in the VCPU or softirq context. Testing: netperf TCP RR - should be improved drastically netperf TCP STREAM guest to host - no regression Contact: MST --- I am trying to make some contributions to improving netperf TCP_RR. Could you please share more ideas or plans or implemental details to make it happen? Thanks, Like Xu