From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f69.google.com (mail-it0-f69.google.com [209.85.214.69]) by kanga.kvack.org (Postfix) with ESMTP id 7909F6B0005 for ; Wed, 14 Feb 2018 13:12:10 -0500 (EST) Received: by mail-it0-f69.google.com with SMTP id d137so11101496itc.0 for ; Wed, 14 Feb 2018 10:12:10 -0800 (PST) Received: from aserp2120.oracle.com (aserp2120.oracle.com. [141.146.126.78]) by mx.google.com with ESMTPS id o205si6699545itd.161.2018.02.14.10.12.09 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 14 Feb 2018 10:12:09 -0800 (PST) Subject: Re: [RFC PATCH V2 00/22] Intel(R) Resource Director Technology Cache Pseudo-Locking enabling References: From: Mike Kravetz Message-ID: Date: Wed, 14 Feb 2018 10:12:03 -0800 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Reinette Chatre , tglx@linutronix.de, fenghua.yu@intel.com, tony.luck@intel.com Cc: gavin.hindman@intel.com, vikas.shivappa@linux.intel.com, dave.hansen@intel.com, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Michal Hocko , Vlastimil Babka On 02/13/2018 07:46 AM, Reinette Chatre wrote: > Adding MM maintainers to v2 to share the new MM change (patch 21/22) that > enables large contiguous regions that was created to support large Cache > Pseudo-Locked regions (patch 22/22). This week MM team received another > proposal to support large contiguous allocations ("[RFC PATCH 0/3] > Interface for higher order contiguous allocations" at > http://lkml.kernel.org/r/20180212222056.9735-1-mike.kravetz@oracle.com). > I have not yet tested with this new proposal but it does seem appropriate > and I should be able to rework patch 22 from this series on top of that if > it is accepted instead of what I have in patch 21 of this series. > Well, I certainly would prefer the adoption and use of a more general purpose interface rather than exposing alloc_gigantic_page(). Both the interface I suggested and alloc_gigantic_page end up calling alloc_contig_range(). I have not looked at your entire patch series, but do be aware that in its present form alloc_contig_range will run into issues if called by two threads simultaneously for the same page range. Calling alloc_gigantic_page without some form of synchronization will expose this issue. Currently this is handled by hugetlb_lock for all users of alloc_gigantic_page. If you simply expose alloc_gigantic_page without any type of synchronization, you may run into issues. The first patch in my RFC "mm: make start_isolate_page_range() fail if already isolated" should handle this situation IF we decide to expose alloc_gigantic_page (which I do not suggest). -- Mike Kravetz -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org