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=-4.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 D0C3FC4727E for ; Wed, 7 Oct 2020 16:30:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4FA6B20708 for ; Wed, 7 Oct 2020 16:30:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="bjsK0aDx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727997AbgJGQak (ORCPT ); Wed, 7 Oct 2020 12:30:40 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:36186 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727990AbgJGQaj (ORCPT ); Wed, 7 Oct 2020 12:30:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1602088238; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=EnhQBerWUQ4B1SJXlk0CfeVXcWu6CUN1xfdJTyciM6A=; b=bjsK0aDxcdUTEr2CWSmHkoxcoH89XZYHOgoLUSlVE6W7CB/2kfm83A2ZEWXtEC7Y8FpRVy wcTOpsXKqzdH/VgyL7egJJ+msarbMPuNZPCGqWaKVBlk7O0rLG6L8xzNw3oJPCNz+QhFNx rykLjjE5hnhPw+kc0i86GxtGa+ypA2o= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-495-rfEf73lmMKCcsCcKfhFZxw-1; Wed, 07 Oct 2020 12:30:36 -0400 X-MC-Unique: rfEf73lmMKCcsCcKfhFZxw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 202328797F0; Wed, 7 Oct 2020 16:30:35 +0000 (UTC) Received: from [172.16.176.1] (ovpn-64-66.rdu2.redhat.com [10.10.64.66]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 964515DA76; Wed, 7 Oct 2020 16:30:34 +0000 (UTC) From: "Benjamin Coddington" To: "Patrick Goetz" Cc: "J. Bruce Fields" , linux-nfs@vger.kernel.org Subject: Re: unsharing tcp connections from different NFS mounts Date: Wed, 07 Oct 2020 12:30:33 -0400 Message-ID: In-Reply-To: References: <20201006151335.GB28306@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On 7 Oct 2020, at 9:56, Patrick Goetz wrote: > On 10/6/20 10:13 AM, J. Bruce Fields wrote: >> NFSv4.1+ differs from earlier versions in that it always performs >> trunking discovery that results in mounts to the same server sharing a >> TCP connection. >> >> It turns out this results in performance regressions for some users; >> apparently the workload on one mount interferes with performance of >> another mount, and they were previously able to work around the problem >> by using different server IP addresses for the different mounts. >> >> Am I overlooking some hack that would reenable the previous behavior? >> Or would people be averse to an "-o noshareconn" option? >> >> --b. >> > > > I don't see how sharing a TCP connection can result in a performance > regression (the performance degradation of *not* sharing a TCP connection > is why HTTP 1.x is being replaced), or how using different IP addresses on > the same interface resolves anything. Does anyone have an explanation? Well, I think the report we're getting may be using two different network interfaces on the server-side. The user was previously doing one mount each to each ip address on each interface. Even if you don't have this arrangement, it may still be possible/desirable to have separate TCP connections if you want to prioritizes some NFS traffic. Multi-CPU systems with modern NICs have a number of different ways to "steer" the traffic they receive to certain CPUs which may have a benefit or detrimental effect on performance. You can prioritize wake-ups from the NIC based on throughput or latency, for example. I don't know for sure which of these specific details are coming into play, if any, though. Ben