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=-12.8 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1, USER_IN_DEF_DKIM_WL 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 2F028C433DF for ; Thu, 9 Jul 2020 21:49:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 03E2220786 for ; Thu, 9 Jul 2020 21:49:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="npT9p+MK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726446AbgGIVtj (ORCPT ); Thu, 9 Jul 2020 17:49:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59302 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726193AbgGIVtj (ORCPT ); Thu, 9 Jul 2020 17:49:39 -0400 Received: from mail-pj1-x1041.google.com (mail-pj1-x1041.google.com [IPv6:2607:f8b0:4864:20::1041]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 09354C08C5CE for ; Thu, 9 Jul 2020 14:49:39 -0700 (PDT) Received: by mail-pj1-x1041.google.com with SMTP id mn17so1698534pjb.4 for ; Thu, 09 Jul 2020 14:49:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:in-reply-to:message-id:references :user-agent:mime-version; bh=hFr4sv4HqUSHsiMLFrScOT9Ngpz9Cto5b81cd6f0i7M=; b=npT9p+MKNUWXQYWnllvP0dSbLmAXzhuZ/YaLbF3/8MW4bc+uhAX1qaA89d9JVJxBR6 PbUgRXSVwJZeFnp0E9X5JZoApnSJT0NfL23ffg22fwzr5sxzXEzHcL/uaMA6f5Ni2Acd zT37F2Hko+N8k9JdOa4Txvp0uVcibFkV+cndLptq13d8npFhI8UlM2fR2zoAjgawPoTi eTPoxLFxZ3n/VbBci5vXHlMUlSvVgr/66p04oUNOMaidVbaLVmcpnaoKHdWCcCCq+jkA qtaAbzyPWkqMl390vWaIOCRnfftDYD1rUZt8xxobcI7XIrplNI2Xvy5x6HaBo4NjhGMZ L3UQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version; bh=hFr4sv4HqUSHsiMLFrScOT9Ngpz9Cto5b81cd6f0i7M=; b=oTf7dpwBLozWl4zIK/rw4Avic0ArhQrxJAH7cGLb65HaAcwJZf3qCt2VZCxDgz5aoj ptN9dJV5Kw7q//nSFKjVm5Vfq2aZTZuZaUuz3lRQtUu/vRcgrkuyu0OFuV/sVm1kEXcm fUueTeyfGXmLBVRz6Ze2/Xj5I6kJAfnrBG9UlB1TkwwYAQQLRNO1tNOKFZSApQuheLQF YyoJO34Nm9Jt05RObexrXkwWBnrkA85NdCA6n5fMjstS27d9c46Nl5JHT7KVZeNZf0lT eAhSbGkheyi14Z5+6jzWzt6O54fncGWsHoO6xhuQTsk9wjYjSyteYbMO9NlkCuEim2Z/ gXBQ== X-Gm-Message-State: AOAM533VwgPIyTLj4gQ8aM0uszYmv2leAcPheetd4JLJXfGoHFGNPRLw 3dLzOBepe67RHmOs9o2v5QkHjw== X-Google-Smtp-Source: ABdhPJxifzME9k8oQf7I8/PrwyXLawsOmZkDIwApjP8xedu3YYKr6okgkKrdw3W2Hz9t2cE8c+Pk6Q== X-Received: by 2002:a17:90b:3c1:: with SMTP id go1mr2110948pjb.129.1594331378329; Thu, 09 Jul 2020 14:49:38 -0700 (PDT) Received: from [2620:15c:17:3:4a0f:cfff:fe51:6667] ([2620:15c:17:3:4a0f:cfff:fe51:6667]) by smtp.gmail.com with ESMTPSA id u74sm3454482pgc.58.2020.07.09.14.49.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Jul 2020 14:49:37 -0700 (PDT) Date: Thu, 9 Jul 2020 14:49:37 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Christoph Hellwig cc: Nicolas Saenz Julienne , Marek Szyprowski , Robin Murphy , linux-rpi-kernel@lists.infradead.org, jeremy.linton@arm.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] dma-pool: use single atomic pool for both DMA zones In-Reply-To: <20200708161010.GA30184@lst.de> Message-ID: References: <20200707122804.21262-1-nsaenzjulienne@suse.de> <20200708153509.GA26743@lst.de> <20200708161010.GA30184@lst.de> User-Agent: Alpine 2.23 (DEB 453 2020-06-18) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 8 Jul 2020, Christoph Hellwig wrote: > On Wed, Jul 08, 2020 at 06:00:35PM +0200, Nicolas Saenz Julienne wrote: > > On Wed, 2020-07-08 at 17:35 +0200, Christoph Hellwig wrote: > > > On Tue, Jul 07, 2020 at 02:28:04PM +0200, Nicolas Saenz Julienne wrote: > > > > When allocating atomic DMA memory for a device, the dma-pool core > > > > queries __dma_direct_optimal_gfp_mask() to check which atomic pool to > > > > use. It turns out the GFP flag returned is only an optimistic guess. > > > > The pool selected might sometimes live in a zone higher than the > > > > device's view of memory. > > > > > > > > As there isn't a way to grantee a mapping between a device's DMA > > > > constraints and correct GFP flags this unifies both DMA atomic pools. > > > > The resulting pool is allocated in the lower DMA zone available, if any, > > > > so as for devices to always get accessible memory while having the > > > > flexibility of using dma_pool_kernel for the non constrained ones. > > > > > > > > Fixes: c84dc6e68a1d ("dma-pool: add additional coherent pools to map to gfp > > > > mask") > > > > Reported-by: Jeremy Linton > > > > Suggested-by: Robin Murphy > > > > Signed-off-by: Nicolas Saenz Julienne > > > > > > Hmm, this is not what I expected from the previous thread. I thought > > > we'd just use one dma pool based on runtime available of the zones.. > > > > I may be misunderstanding you, but isn't that going back to how things used to > > be before pulling in David Rientjes' work? The benefit of having a GFP_KERNEL > > pool is that non-address-constrained devices can get their atomic memory there, > > instead of consuming somewhat scarcer low memory. > > Yes, I think we are misunderstanding each other. I don't want to remove > any pool, just make better runtime decisions when to use them. > Just to be extra explicit for the record and for my own understanding: Nicolas, your patch series "dma-pool: Fix atomic pool selection" obsoletes this patch, right? :)