Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A2401C433F5 for ; Wed, 15 Dec 2021 07:03:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236076AbhLOHDo (ORCPT ); Wed, 15 Dec 2021 02:03:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33032 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235852AbhLOHDn (ORCPT ); Wed, 15 Dec 2021 02:03:43 -0500 Received: from mail-pj1-x1034.google.com (mail-pj1-x1034.google.com [IPv6:2607:f8b0:4864:20::1034]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2E528C061574; Tue, 14 Dec 2021 23:03:43 -0800 (PST) Received: by mail-pj1-x1034.google.com with SMTP id k6-20020a17090a7f0600b001ad9d73b20bso18318570pjl.3; Tue, 14 Dec 2021 23:03:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=aFB3zrYvsnnfO0vx/SsksAk1QGRVLRM3ofNufeo+PJc=; b=YzoB6yjvezFylfMhN8lj8gq+BNBJ1JsI/Rm+zpii6DX3Ias5Xk+0QhmtIMZjCDWTE2 wfnDntdkMKC2SLG835hKNe3ElO7yuQ1K7lmboOzGFvz8lnHm7UXnZj1TvLzFZR9w3ntR Hx9aJBndr4XhaxUqfbNQQ2eD8gAd6sGuwkXgEk372lmRUpPKRsb//DL8dJ1EZkhRppl/ MJ4m4a8Pj4aVn7QwYLArAxYdeutnvmeiVaxnw47iP/y5yMeLBfx9VzS16IZ60NBKtZMn /TQXthNmZ9SyBB7OSgPd5cLbQ7qS8fHFnaB1mrfNT76KdfXSz59MivWYSjvssbDUF50b ZcaA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=aFB3zrYvsnnfO0vx/SsksAk1QGRVLRM3ofNufeo+PJc=; b=h9C+lAGGvagEsHEKSRrml52Rfq8ORPh+ox7bKB/JsSwiBVi69yzyA9cQ+mC47/IQsC FJex4IflznCTx/CYoH3ip3EnBGDdNxspEa+rPwtWROvYmEc0mu9C/ISfyt+hKPEWho3Y RxL7ldB7KI91WHBtdYpQGZMbmVz4iCZCY66o0zwhEDTfdcH7iv13DC6hRpe/8a4MBOTt VHXNTlJX81WTnSeD49TDc2/odSlT1nhjM8cW818PAfJxYpBziLedzTOxQYx7PO1iPGP6 dORPcLizX5KMNJvQ9GdiBdVW0uYOMAc1mr+1E10yi8vLKvOf1uPM1uZheH6QlU57nKw/ GJtw== X-Gm-Message-State: AOAM530HitcaAXIM7PatfTSwCUDWXOFnh1auIU8U9gmkNh3NmPIOJqvn Yxni3PJANP13uDMG8veV8+A= X-Google-Smtp-Source: ABdhPJymvszIJp5x2/rZeDDSbk1JK+ZtC9yjHhRIlBi6dDcZVrDHByKhpmjFbx2JeAs8ETva/J7kqg== X-Received: by 2002:a17:902:6b47:b0:142:82e1:6c92 with SMTP id g7-20020a1709026b4700b0014282e16c92mr9656466plt.84.1639551822672; Tue, 14 Dec 2021 23:03:42 -0800 (PST) Received: from odroid ([114.29.23.242]) by smtp.gmail.com with ESMTPSA id m6sm1115137pgb.31.2021.12.14.23.03.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Dec 2021 23:03:42 -0800 (PST) Date: Wed, 15 Dec 2021 07:03:35 +0000 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Vlastimil Babka Cc: Baoquan He , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, hch@lst.de, cl@linux.com, John.p.donnelly@oracle.com, kexec@lists.infradead.org, stable@vger.kernel.org, Pekka Enberg , David Rientjes , Joonsoo Kim Subject: Re: [PATCH v3 5/5] mm/slub: do not create dma-kmalloc if no managed pages in DMA zone Message-ID: <20211215070335.GA1165926@odroid> References: <20211213122712.23805-1-bhe@redhat.com> <20211213122712.23805-6-bhe@redhat.com> <20211213134319.GA997240@odroid> <20211214053253.GB2216@MiWiFi-R3L-srv> <20211215044818.GB1097530@odroid> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211215044818.GB1097530@odroid> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 15, 2021 at 04:48:26AM +0000, Hyeonggon Yoo wrote: > > Hello Baoquan and Vlastimil. > > I'm not sure allowing ZONE_DMA32 for kdump kernel is nice way to solve > this problem. Devices that requires ZONE_DMA is rare but we still > support them. > > If we allow ZONE_DMA32 for ZONE_DMA in kdump kernels, > the problem will be hard to find. > Sorry, I sometimes forget validating my english writing :( What I meant: I'm not sure that allocating from ZONE_DMA32 instead of ZONE_DMA for kdump kernel is nice way to solve this problem. Devices that requires ZONE_DMA memory is rare but we still support them. If we use ZONE_DMA32 memory instead of ZONE_DMA in kdump kernels, It will be hard to the problem when we use devices that can use only ZONE_DMA memory. > What about one of those?: > > 1) Do not call warn_alloc in page allocator if will always fail > to allocate ZONE_DMA pages. > > > 2) let's check all callers of kmalloc with GFP_DMA > if they really need GFP_DMA flag and replace those by DMA API or > just remove GFP_DMA from kmalloc() > > 3) Drop support for allocating DMA memory from slab allocator > (as Christoph Hellwig said) and convert them to use DMA32 (as Christoph Hellwig said) and convert them to use *DMA API* > and see what happens > > Thanks, > Hyeonggon. > > > >> > > >> Maybe the function get_capabilities() want to allocate memory > > >> even if it's not from DMA zone, but other callers will not expect that. > > > > > > Yeah, I have the same guess too for get_capabilities(), not sure about other > > > callers. Or, as ChristophL and ChristophH said(Sorry, not sure if this is > > > the right way to call people when the first name is the same. Correct me if > > > it's wrong), any buffer requested from kmalloc can be used by device driver. > > > Means device enforces getting memory inside addressing limit for those > > > DMA transferring buffer which is usually large, Megabytes level with > > > vmalloc() or alloc_pages(), but doesn't care about this kind of small > > > piece buffer memory allocated with kmalloc()? Just a guess, please tell > > > a counter example if anyone happens to know, it could be easy. > > > > > > > > >> > > >> > kmalloc_caches[KMALLOC_DMA][i] = create_kmalloc_cache( > > >> > kmalloc_info[i].name[KMALLOC_DMA], > > >> > kmalloc_info[i].size, > > >> > -- > > >> > 2.17.2 > > >> > > > >> > > > >> > > > > >