From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jiri Pirko Subject: Re: [patch net-next v4 0/4] return offloaded stats as default and expose original sw stats Date: Fri, 17 Jun 2016 16:05:13 +0200 Message-ID: <20160617140512.GB1981@nanopsycho.orion> References: <1466066237-7719-1-git-send-email-jiri@resnulli.us> <20160616.172632.1759391103978744570.davem@davemloft.net> <20160617082411.GA1981@nanopsycho.orion> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Miller , netdev@vger.kernel.org, nogahf@mellanox.com, idosch@mellanox.com, eladr@mellanox.com, yotamg@mellanox.com, ogerlitz@mellanox.com, roopa@cumulusnetworks.com, nikolay@cumulusnetworks.com, linville@tuxdriver.com, tgraf@suug.ch, gospo@cumulusnetworks.com, sfeldma@gmail.com, sd@queasysnail.net, eranbe@mellanox.com, ast@plumgrid.com, edumazet@google.com, hannes@stressinduktion.org, f.fainelli@gmail.com To: David Ahern Return-path: Received: from mail-wm0-f66.google.com ([74.125.82.66]:36092 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752094AbcFQOFQ (ORCPT ); Fri, 17 Jun 2016 10:05:16 -0400 Received: by mail-wm0-f66.google.com with SMTP id m124so46669wme.3 for ; Fri, 17 Jun 2016 07:05:15 -0700 (PDT) Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: Fri, Jun 17, 2016 at 03:48:35PM CEST, dsa@cumulusnetworks.com wrote: >On 6/17/16 2:24 AM, Jiri Pirko wrote: >> >>The problem we try to handle is different, it's about offloaded >>forwarded packets which are not seen by kernel. Let me try to draw it :) >> >> port1 port2 (HW stats are counted here) >> \ / >> \ / >> \ / >> --(A)---- ASIC --(B)-- >> | >> (C) >> | >> CPU (SW stats are counted here) >> >> >>Now we have couple of flows for TX and RX (direction does not matter here): >> >>1) port1->A->ASIC->C->CPU >> >> For this flow, HW and SW stats are equal. >> >>2) port1->A->ASIC->C->CPU->C->ASIC->B->port2 >> >> For this flow, HW and SW stats are equal. >> >>3) port1->A->ASIC->B->port2 >> >> For this flow, SW stats are 0. >> >>The purpose of this patchset is to provide facility for user to >>find out the difference between flows 1+2 and 3. In other words, user >>will be able to see the statistics for his slow-path (through kernel). >> >>Also, as a default the accumulated stats (HW) will be exposed to user >>so the userspace apps can react properly. >> > >You no longer agree with this discussion? > http://comments.gmane.org/gmane.linux.network/346740 > >Essentially netdevice stats show counters for packets punted to the cpu and >ethool -S shows h/w stats. This patch set seems to invert that. That is problematic. Existing apps depend on rtnetlink stats. But if we don't count offloaded forwarded packets, the apps don't see anything. Therefore I believe that this patchset approach is better. The existing apps continue to work and future apps can use newly introduces sw_stats to query slowpath traffic. Makes sense to me.