From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754433AbbAZLyO (ORCPT ); Mon, 26 Jan 2015 06:54:14 -0500 Received: from 8bytes.org ([81.169.241.247]:45958 "EHLO theia.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753823AbbAZLyK (ORCPT ); Mon, 26 Jan 2015 06:54:10 -0500 Date: Mon, 26 Jan 2015 12:54:08 +0100 From: Joerg Roedel To: Baoquan He Cc: Borislav Petkov , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Konrad Rzeszutek Wilk , x86@kernel.org, linux-kernel@vger.kernel.org, Joerg Roedel Subject: Re: [PATCH 2/3] x86, swiotlb: Try coherent allocations with __GFP_NOWARN Message-ID: <20150126115408.GE30345@8bytes.org> References: <1420555874-11506-1-git-send-email-joro@8bytes.org> <1420555874-11506-3-git-send-email-joro@8bytes.org> <20150123170306.GH22635@pd.tnic> <20150126032236.GN2461@dhcp-16-105.nay.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150126032236.GN2461@dhcp-16-105.nay.redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 26, 2015 at 11:22:36AM +0800, Baoquan He wrote: > > Ok, so this practically does all allocations __GFP_NOWARN now. Shouldn't > > you be doing this before swiotlb_alloc_coherent() and not before > > dma_generic_alloc_coherent()? > > I think this patch mainly suppress warning from buddy allocation > failure because it tried buddy allocation several times before the final > try of bounce buffer allocation. Buddy allocation failure will call > dump_stack. Yes, exactly. The default low-memory available to the page-allocator with crashkernel=high is 8MB. This is up pretty fast and then we start to get warnings, even when there is still memory left in the swiotlb space. The __GFP_WARN is there to suppress the warnings from the page-allocator, so it has to be set before it is called. Joerg