From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH net-next 10/31] cxgb4/iw_cxgb4: Doorbell Drop Avoidance Bug Fixes. Date: Thu, 27 Feb 2014 10:21:25 -0800 Message-ID: <20140227102125.5e95620d@nehalam.linuxnetplumber.net> References: <1393427230-14532-11-git-send-email-hariprasad@chelsio.com> <20140226.181216.1563503549713890339.davem@davemloft.net> <005101cf33df$00749e40$015ddac0$@opengridcomputing.com> <20140227.130544.1892840202381139797.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: swise@opengridcomputing.com, hariprasad@chelsio.com, netdev@vger.kernel.org, linux-rdma@vger.kernel.org, roland@purestorage.com, kumaras@chelsio.com, dm@chelsio.com, leedom@chelsio.com, santosh@chelsio.com, nirranjan@chelsio.com To: David Miller Return-path: Received: from mail-pd0-f172.google.com ([209.85.192.172]:52443 "EHLO mail-pd0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752522AbaB0SV3 (ORCPT ); Thu, 27 Feb 2014 13:21:29 -0500 Received: by mail-pd0-f172.google.com with SMTP id p10so2756543pdj.31 for ; Thu, 27 Feb 2014 10:21:29 -0800 (PST) In-Reply-To: <20140227.130544.1892840202381139797.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 27 Feb 2014 13:05:44 -0500 (EST) David Miller wrote: > From: "Steve Wise" > Date: Thu, 27 Feb 2014 11:11:49 -0600 > > >> > >> > -static int allow_db_fc_on_t5; > >> > -module_param(allow_db_fc_on_t5, int, 0644); > >> > -MODULE_PARM_DESC(allow_db_fc_on_t5, > >> > - "Allow DB Flow Control on T5 (default = 0)"); > >> > - > >> > -static int allow_db_coalescing_on_t5; > >> > -module_param(allow_db_coalescing_on_t5, int, 0644); > >> > -MODULE_PARM_DESC(allow_db_coalescing_on_t5, > >> > - "Allow DB Coalescing on T5 (default = 0)"); > >> > >> Module parameters are a user facing interface. > >> > >> You cannot just delete, or change the semantics of, the ones you feel > >> like doing so to. > > > > I see your point on user facing interfaces. These module params were > > added initially to allow tweaking the db drop recovery for T5 devices in > > the thought that we might need it. It turns out T5 doesn't suffer from > > this issue. These params default to 0 anyway, and I doubt anyone has > > changed them. Disabling the hw db coalescing feature proved problematic > > and it turned out to even make the issue worse, so I removed it totally > > at the recommendation from the HW engineers, and put in place the new > > design which better rate controls things under heavy load. > > You have to keep the old ones around. You can keep the parameters but ignore them however.