From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: Re: [net-next-2.6 PATCH] net: netif_set_real_num_rx_queues may cap num_rx_queues at init time Date: Wed, 06 Oct 2010 16:07:13 +0100 Message-ID: <1286377633.2371.11.camel@achroite.uk.solarflarecom.com> References: <20101004220042.3471.92774.stgit@jf-dev1-dcblab> <1286256926.2457.2.camel@edumazet-laptop> <4CAB4D8F.8080108@intel.com> <1286296476.2307.5.camel@achroite.uk.solarflarecom.com> <4CAB6447.6040407@intel.com> <4CAC8D11.2060604@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Eric Dumazet , "netdev@vger.kernel.org" , "therbert@google.com" To: John Fastabend Return-path: Received: from mail.solarflare.com ([216.237.3.220]:34533 "EHLO exchange.solarflare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932440Ab0JFPHR (ORCPT ); Wed, 6 Oct 2010 11:07:17 -0400 In-Reply-To: <4CAC8D11.2060604@intel.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 2010-10-06 at 07:52 -0700, John Fastabend wrote: > On 10/5/2010 10:45 AM, John Fastabend wrote: > > On 10/5/2010 9:34 AM, Ben Hutchings wrote: > >> On Tue, 2010-10-05 at 09:08 -0700, John Fastabend wrote: > >>> On 10/4/2010 10:35 PM, Eric Dumazet wrote: [...] > >>>> Why should we keep num_rx_queues > real_num_rx_queues ? > >>>> > >>> > >>> If we do not ever need them then we should not keep them I agree. > >>> But having netif_set_real_num_rx_queues set something other then > >>> 'real_num_rx_queues' does not seem right to me at least. Also > >>> netif_set_real_num_tx_queues and netif_set_real_num_rx_queues have > >>> different behavior. It would be nice if this weren't the case but > >>> they allocate queues in two places. > >> [...] > >> > >> I only did this to satisfy Eric's desire to reduce memory usage. > >> However, I believe that there are currently no drivers that dynamically > >> increase numbers of RX or TX queues. Until there are, there is not much > >> point in removing this assignment to num_rx_queues. > >> > >> Ben. > >> > > > > ixgbe increases the real_num_[rx|tx]_queues when FCoE or DCB is enabled. > > Also many of the drivers could increase the number of queues if they were > > given more interrupt vectors at some point. > > > If I update the handful drivers that use netif_set_real_num_rx_queues() > before the netdevice is registered to explicitly set num_rx_queues this > would address Eric's concerns and fix drivers that really only want to set > real_num_rx_queue. > > Any thoughts? Don't add assignments to num_rx_queues. If it's useful to increase the number of RX queues later then just remove the assignment to num_rx_queues from netif_set_real_num_rx_queues() and be done with it. The waste of memory is minimal now that we only allocate kobjects for real_num_rx_queues. Ben. -- Ben Hutchings, Senior Software Engineer, Solarflare Communications Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked.