From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Samudrala, Sridhar" Subject: Re: [RFC PATCH] net: Introduce a socket option to enable picking tx queue based on rx queue. Date: Mon, 11 Sep 2017 23:27:13 -0700 Message-ID: References: <1504222032-6337-1-git-send-email-sridhar.samudrala@intel.com> <1505188437.15310.137.camel@edumazet-glaptop3.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Alexander Duyck , Linux Kernel Network Developers To: Eric Dumazet , Tom Herbert Return-path: Received: from mga03.intel.com ([134.134.136.65]:32432 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750911AbdILG1P (ORCPT ); Tue, 12 Sep 2017 02:27:15 -0400 In-Reply-To: <1505188437.15310.137.camel@edumazet-glaptop3.roam.corp.google.com> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 9/11/2017 8:53 PM, Eric Dumazet wrote: > On Mon, 2017-09-11 at 20:12 -0700, Tom Herbert wrote: > >> Two ints in sock_common for this purpose is quite expensive and the >> use case for this is limited-- even if a RX->TX queue mapping were >> introduced to eliminate the queue pair assumption this still won't >> help if the receive and transmit interfaces are different for the >> connection. I think we really need to see some very compelling results >> to be able to justify this. Will try to collect and post some perf data with symmetric queue configuration. > Yes, this is unreasonable cost. > > XPS should really cover the case already. > Eric, Can you clarify how XPS covers the RX-> TX queue mapping case? Is it possible to configure XPS to select TX queue based on the RX queue of a flow? IIUC, it is based on the CPU of the thread doing the transmit OR based on skb->priority to TC mapping? It may be possible to get this effect if the the threads are pinned to a core, but if the app threads are freely moving, i am not sure how XPS can be configured to select the TX queue based on the RX queue of a flow. Thanks Sridhar