From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753048AbbE0SMy (ORCPT ); Wed, 27 May 2015 14:12:54 -0400 Received: from shards.monkeyblade.net ([149.20.54.216]:37886 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751726AbbE0SMw (ORCPT ); Wed, 27 May 2015 14:12:52 -0400 Date: Wed, 27 May 2015 14:12:48 -0400 (EDT) Message-Id: <20150527.141248.2127547726940414483.davem@davemloft.net> To: kys@microsoft.com Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, devel@linuxdriverproject.org, olaf@aepfle.de, apw@canonical.com, jasowang@redhat.com Subject: Re: [PATCH net-next 1/1] hv_netvsc: Properly size the vrss queues From: David Miller In-Reply-To: <1432682469-15033-1-git-send-email-kys@microsoft.com> References: <1432682469-15033-1-git-send-email-kys@microsoft.com> X-Mailer: Mew version 6.6 on Emacs 24.5 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Wed, 27 May 2015 11:12:52 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "K. Y. Srinivasan" Date: Tue, 26 May 2015 16:21:09 -0700 > The current algorithm for deciding on the number of VRSS channels is > not optimal since we open up the min of number of CPUs online and the > number of VRSS channels the host is offering. So on a 32 VCPU guest > we could potentially open 32 VRSS subchannels. Experimentation has > shown that it is best to limit the number of VRSS channels to the number > of CPUs within a NUMA node. As part of this work introduce a module > parameter to control the number of sub-channels we would open up as well. > Here is the new algorithm for deciding on the number of sub-channels we > would open up: > 1) Pick the minimum of what the host is offering and what the driver > in the guest is specifying via the module parameter. > 2) Pick the minimum of (1) and the numbers of CPUs in the NUMA > node the primary channel is bound to. > > Signed-off-by: K. Y. Srinivasan No new module parameters, sorry. You will have to make it such that this can be changed at run time, and use a generic run-time mechanism to configure this value that any driver can use. I will not accept: "this is not possible" or "this is too hard" as a reason why you have to use a module parameter. Settings that cannot be set at run time are painful for people who run large scale operations where resetting entire systems to change a setting is completely and utterly impractical.