From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f70.google.com (mail-wm0-f70.google.com [74.125.82.70]) by kanga.kvack.org (Postfix) with ESMTP id E44A16B0499 for ; Fri, 25 Aug 2017 17:50:01 -0400 (EDT) Received: by mail-wm0-f70.google.com with SMTP id t138so1284137wmt.6 for ; Fri, 25 Aug 2017 14:50:01 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id m188si1843131wme.155.2017.08.25.14.50.00 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 25 Aug 2017 14:50:00 -0700 (PDT) Date: Fri, 25 Aug 2017 14:49:57 -0700 From: Andrew Morton Subject: Re: [RFC PATCH] mm: fadvise: avoid fadvise for fs without backing device Message-Id: <20170825144957.5d99dad605fed1dc2550d25c@linux-foundation.org> In-Reply-To: References: <20170818011023.181465-1-shakeelb@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Shakeel Butt Cc: Mel Gorman , Johannes Weiner , Hillf Danton , Vlastimil Babka , Hugh Dickins , Greg Thelen , Linux MM , LKML On Thu, 17 Aug 2017 18:20:17 -0700 Shakeel Butt wrote: > +linux-mm, linux-kernel > > On Thu, Aug 17, 2017 at 6:10 PM, Shakeel Butt wrote: > > The fadvise() manpage is silent on fadvise()'s effect on > > memory-based filesystems (shmem, hugetlbfs & ramfs) and pseudo > > file systems (procfs, sysfs, kernfs). The current implementaion > > of fadvise is mostly a noop for such filesystems except for > > FADV_DONTNEED which will trigger expensive remote LRU cache > > draining. This patch makes the noop of fadvise() on such file > > systems very explicit. > > > > However this change has two side effects for ramfs and one for > > tmpfs. First fadvise(FADV_DONTNEED) can remove the unmapped clean > > zero'ed pages of ramfs (allocated through read, readahead & read > > fault) and tmpfs (allocated through read fault). Also > > fadvise(FADV_WILLNEED) on create such clean zero'ed pages for > > ramfs. That sentence makes no sense. I assume "fadvise(FADV_WILLNEED) will create"? -- 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