From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sat, 21 Apr 2007 08:37:03 +0100 (BST) From: Hugh Dickins Subject: Re: [PATCH] lazy freeing of memory through MADV_FREE 2/2 In-Reply-To: Message-ID: References: <46247427.6000902@redhat.com> <4627DBF0.1080303@redhat.com> <20070420140316.e0155e7d.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Ulrich Drepper Cc: Andrew Morton , Rik van Riel , Jakub Jelinek , linux-kernel , linux-mm List-ID: On Fri, 20 Apr 2007, Ulrich Drepper wrote: > > Just for reference: the MADV_CURRENT behavior is to throw away data in > the range. Not exactly. The Linux MADV_DONTNEED never throws away data from a PROT_WRITE,MAP_SHARED mapping (or shm) - it propagates the dirty bit, the page will eventually get written out to file, and can be retrieved later by subsequent access. But the Linux MADV_DONTNEED does throw away data from a PROT_WRITE,MAP_PRIVATE mapping (or brk or stack) - those changes are discarded, and a subsequent access will revert to zeroes or the underlying mapped file. Been like that since before 2.4.0. > The POSIX_MADV_DONTNEED behavior is to never lose data. > I.e., file backed data is written back, anon data is at most swapped > out. -- 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