From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Kravetz Subject: Re: [RFC] mmap(MAP_CONTIG) Date: Wed, 4 Oct 2017 10:38:57 -0700 Message-ID: <434a5870-0115-b8ab-bd6c-b7f4db847dc4@oracle.com> References: <21f1ec96-2822-1189-1c95-79a2bb491571@oracle.com> <97c81533-5206-b130-1aeb-c5b9bfd93287@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US Sender: owner-linux-mm@kvack.org To: Christopher Lameter , Anshuman Khandual Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Marek Szyprowski , Michal Nazarewicz , "Aneesh Kumar K.V" , Joonsoo Kim , Guy Shattah List-Id: linux-api@vger.kernel.org On 10/04/2017 09:05 AM, Christopher Lameter wrote: > On Wed, 4 Oct 2017, Anshuman Khandual wrote: > >>> - Using 'pre-allocated' pages in the fault paths may be intrusive. >> >> But we have already faulted in all of them for the mapping and they >> are also locked. Hence there should not be any page faults any more >> for the VMA. Am I missing something here ? > > The PTEs may be torn down and have to reestablished through a page faults. > Page faults would not allocate memory. > >> I am still wondering why wait till fault time not pre fault all of them >> and populate the page tables. > > They are populated but some processes (swap and migration) may tear them > down. As mentioned in my reply to Anshuman, the mention of fault paths here may be a source of confusion. I would expect the entire mapping to be populated at mmap time, and the pages locked. Therefore, there should be no swap or migration. -- 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