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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 42AB5C04EB9 for ; Mon, 3 Dec 2018 17:33:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1A7FE20850 for ; Mon, 3 Dec 2018 17:33:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1A7FE20850 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726906AbeLCRd3 (ORCPT ); Mon, 3 Dec 2018 12:33:29 -0500 Received: from verein.lst.de ([213.95.11.211]:38579 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725897AbeLCRd3 (ORCPT ); Mon, 3 Dec 2018 12:33:29 -0500 Received: by newverein.lst.de (Postfix, from userid 2407) id 50D8268AFE; Mon, 3 Dec 2018 18:33:22 +0100 (CET) Date: Mon, 3 Dec 2018 18:33:22 +0100 From: Christoph Hellwig To: John Garry Cc: Christoph Hellwig , Robin Murphy , Qian Cai , netdev@vger.kernel.org, linuxarm@huawei.com, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, yisen.zhuang@huawei.com Subject: Re: [PATCH] dma-debug: Kconfig for PREALLOC_DMA_DEBUG_ENTRIES Message-ID: <20181203173322.GB8282@lst.de> References: <20181130175449.2625-1-cai@gmx.us> <20181201163657.GA19557@lst.de> <53ab96d7-5dc9-e1a9-4cf2-bb8bf80a3acf@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53ab96d7-5dc9-e1a9-4cf2-bb8bf80a3acf@huawei.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 03, 2018 at 11:56:11AM +0000, John Garry wrote: > On 01/12/2018 16:36, Christoph Hellwig wrote: >> On Fri, Nov 30, 2018 at 07:39:50PM +0000, Robin Murphy wrote: >>> I was assuming the point was to also add something like >>> >>> default 131072 if HNS_ENET >>> >>> so that DMA debug doesn't require too much thought from the user. If they >>> still have to notice the overflow message and empirically figure out a >>> value that does work, rebuilding the kernel each time is far less >>> convenient than simply adding "dma_debug_entries=..." to their kernel >>> command line and rebooting, which they can do today. If they do already >>> know up-front that the default will need overriding and what the >>> appropriate value is, then the command line still seems seems just as >>> convenient. >> >> I'm not so fond of random drivers changing the defaults. My idea >> was rather to have the config option so that the defconfig files for >> the Hisilicon SOCs with this hardware could select a larger number >> without making a total mess of the kernel configuration. >> >> If we really have to we could do different defaults, but I'd still >> much rather do this on a arch/platform basis than specific drivers. > > As I understand, some drivers could even use much more than this (131072), > to such a point where I can't imagine that we would want to set an arch > default to support them. For this HNS_ENET case, it is arm64 specific so it > would be an arch defconfig. But I'm not sure we could always do the right thing for everyone. I think we might be better of trying to just dynamically allocate entries when we run out of them instead of coming up with a perfect number.