From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6C296C43461 for ; Tue, 15 Sep 2020 08:26:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 455B2221E7 for ; Tue, 15 Sep 2020 08:26:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726185AbgIOI0C (ORCPT ); Tue, 15 Sep 2020 04:26:02 -0400 Received: from stargate.chelsio.com ([12.32.117.8]:27526 "EHLO stargate.chelsio.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726260AbgIOIL2 (ORCPT ); Tue, 15 Sep 2020 04:11:28 -0400 Received: from localhost ([10.193.186.242]) by stargate.chelsio.com (8.13.8/8.13.8) with ESMTP id 08F8Asku001472; Tue, 15 Sep 2020 01:10:55 -0700 Date: Tue, 15 Sep 2020 13:40:54 +0530 From: Potnuri Bharat Teja To: Leon Romanovsky Cc: "jgg@ziepe.ca" , "dledford@redhat.com" , "linux-rdma@vger.kernel.org" Subject: Re: [PATCH] RDMA/iw_cxgb4: disable delayed ack by default Message-ID: <20200915081049.GA21844@chelsio.com> References: <20200909134726.10348-1-bharat@chelsio.com> <20200910122739.GJ421756@unreal> <20200911131152.GM421756@unreal> <20200911160951.GA20264@chelsio.com> <20200913071325.GC35718@unreal> <20200914170116.GA14572@chelsio.com> <20200915064706.GH35718@unreal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200915064706.GH35718@unreal> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On Tuesday, September 09/15/20, 2020 at 12:17:06 +0530, Leon Romanovsky wrote: > On Mon, Sep 14, 2020 at 10:31:17PM +0530, Potnuri Bharat Teja wrote: > > On Sunday, September 09/13/20, 2020 at 12:43:25 +0530, Leon Romanovsky wrote: > > > On Fri, Sep 11, 2020 at 09:39:57PM +0530, Potnuri Bharat Teja wrote: > > > > On Friday, September 09/11/20, 2020 at 18:41:52 +0530, Leon Romanovsky wrote: > > > > > On Thu, Sep 10, 2020 at 07:14:50PM +0000, Potnuri Bharat Teja wrote: > > > > > > >> Subject: [PATCH] RDMA/iw_cxgb4: disable delayed ack by default > > > > > > >> > > > > > > >> Receive side delayed ack mode is needed only for certain area networks/ connections. Therefore disable it by default. > > > > > > >> > > > > > > >> Signed-off-by: Potnuri Bharat Teja > > > > > > >> --- > > > > > > >> drivers/infiniband/hw/cxgb4/cm.c | 4 ++-- > > > > > > >> 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > >> > > > > > > >> diff --git a/drivers/infiniband/hw/cxgb4/cm.c b/drivers/infiniband/hw/cxgb4/cm.c > > > > > > >> index 1f288c73ccfc..8769e7aa097f 100644 > > > > > > >> --- a/drivers/infiniband/hw/cxgb4/cm.c > > > > > > >> +++ b/drivers/infiniband/hw/cxgb4/cm.c > > > > > > >> @@ -77,9 +77,9 @@ static int enable_ecn; module_param(enable_ecn, int, 0644); MODULE_PARM_DESC(enable_ecn, "Enable ECN (default=0/disabled)"); > > > > > > >> > > > > > > >> -static int dack_mode = 1; > > > > > > >> +static int dack_mode; > > > > > > >> module_param(dack_mode, int, 0644); > > > > > > >> -MODULE_PARM_DESC(dack_mode, "Delayed ack mode (default=1)"); > > > > > > >> +MODULE_PARM_DESC(dack_mode, "Delayed ack mode (default=0)"); > > > > > > > > > > > > > >Are you sure that this doesn't break user scripts? > > > > > > Yes, I am sure. This does not interfere with user/kernel RDMA functionalities. > > > > > > > > > > How is it possible? > > > > > Before this change user that did "modprobe iw_cxgb4" had delayed mode > > > > > enabled, after this he will need to issue "modprobe iw_cxgb4 dack_mode=1" > > > > > > > > > Sorry I didnt get it right earlier. Yes now if user wants delayed ack mode, > > > > user can issue "modprobe iw_cxgb4 dack_mode=1" or change it dynamically via > > > > /sys/module/<>/paramters. > > > > Chelsio adapters for better performance in most cases needs delayed ack mode to > > > > be disabled. This change somehow got missed upstream all this while. > > > > In fewer explicit cases, user can enable delayed ack mode where it is needed. > > > > > > So why doesn't rdma-core have dack_mode=0 in kernel-boot scripts? > > > > > Do you mean why dont I simply change rdma-hw-modules.rules instead? > > I could do that if this is a user mode only setting. But this is needed for kernel > > mode too where in some cases rdma-core may not be installed. > > No, I'm asking why if "dack_mode=0" is better and preferable way to > operate, it was never set in rdma-core. > Found this only recently that it was wrongly enabled by default which affects severely the performance of some of our adapters with low HW resources for larger IO sizes. I could have mentioned this in commit description but I thought it's a trivial change code wise. > I'm not saying that your kernel patch is wrong, just trying to get sense > on implications for the rdma-core. > ok. yes rdma-hw-modules.rules provides a cleaner way. I am still used to setting module params via /sys/module/<>/parameters/*. Thanks for the review.