From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH v3 net] net: solve a NAPI race Date: Mon, 27 Feb 2017 15:23:15 -0800 Message-ID: <20170227152315.7e3b284f@xeon-e3> References: <20170227141403.714490f7@xeon-e3> <1488234917.9415.217.camel@edumazet-glaptop3.roam.corp.google.com> <20170227144455.174ab1e5@xeon-e3> <20170227.174854.1727197935165904806.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: eric.dumazet@gmail.com, netdev@vger.kernel.org To: David Miller Return-path: Received: from mail-pg0-f50.google.com ([74.125.83.50]:36742 "EHLO mail-pg0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751392AbdB1BSG (ORCPT ); Mon, 27 Feb 2017 20:18:06 -0500 Received: by mail-pg0-f50.google.com with SMTP id s67so50990999pgb.3 for ; Mon, 27 Feb 2017 17:17:52 -0800 (PST) In-Reply-To: <20170227.174854.1727197935165904806.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 27 Feb 2017 17:48:54 -0500 (EST) David Miller wrote: > From: Stephen Hemminger > Date: Mon, 27 Feb 2017 14:44:55 -0800 > > > On Mon, 27 Feb 2017 14:35:17 -0800 > > Eric Dumazet wrote: > > > >> On Mon, 2017-02-27 at 14:14 -0800, Stephen Hemminger wrote: > >> > >> > The original design (as Davem mentioned) was that IRQ's must be disabled > >> > during device polling. If that was true, then the race above > >> > would be impossible. > >> > >> I would love to see an alternative patch. > > > > Turn off busy poll? > > The poll stuff runs risk of breaking more things. > > Eric is exactly trying to make busy poll even more prominent in > the stack, not less prominent. > > It's an important component of some performance improvements he is > working on. Maybe making IRQ controlled as part of the network device model (instead of a side effect left to device driver to handle) would be less problematic. Really just shooting in the dark because I don't have any of the problematic hardware to play with.