From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id 2D5906B0047 for ; Tue, 31 Mar 2009 12:25:40 -0400 (EDT) Date: Tue, 31 Mar 2009 18:25:25 +0200 From: Andrea Arcangeli Subject: Re: [PATCH 4/4] add ksm kernel shared memory driver. Message-ID: <20090331162525.GU9137@random.random> References: <1238457560-7613-5-git-send-email-ieidus@redhat.com> <49D17C04.9070307@codemonkey.ws> <49D20B63.8020709@redhat.com> <49D21B33.4070406@codemonkey.ws> <20090331142533.GR9137@random.random> <49D22A9D.4050403@codemonkey.ws> <20090331150218.GS9137@random.random> <49D23224.9000903@codemonkey.ws> <20090331151845.GT9137@random.random> <49D23CD1.9090208@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <49D23CD1.9090208@codemonkey.ws> Sender: owner-linux-mm@kvack.org To: Anthony Liguori Cc: Izik Eidus , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, avi@redhat.com, chrisw@redhat.com, riel@redhat.com, jeremy@goop.org, mtosatti@redhat.com, hugh@veritas.com, corbet@lwn.net, yaniv@redhat.com, dmonakhov@openvz.org List-ID: On Tue, Mar 31, 2009 at 10:54:57AM -0500, Anthony Liguori wrote: > You can still disable ksm and simply return ENOSYS for the MADV_ flag. You -EINVAL if something, -ENOSYS would tell userland that it shall stop trying to use madvise, including the other MADV_ too. > could even keep it as a module if you liked by separating the madvise bits > from the ksm bits. The madvise() bits could just provide the tracking > infrastructure for determine which vmas were currently marked as sharable. > You could then have ksm as loadable module that consumed that interface to > then perform scanning. What's the point of making ksm a module if one has part of ksm code loaded in the kernel and not being possible to avoid compiling in? People that says KSM=N in their .config (like embedded running with 1M of ram), don't want that tracking overhead compiled into the kernel. Returning -EINVAL would be an option but again I think madvise is core syscall for SuS and I don't like that those core VM parts returns -EINVAL at will depend on certain kernel modules being loaded. > A number of MADV_ flags are Linux specific (like > MADV_DOFORK/MADV_DONTFORK). But those aren't kernel module related, so they're in line with the standard ones and could be adapted by other OS. KSM is not a core VM functionality, madvise is a core VM functionality, so I don't see fit. KSM as ioctl or KSM creating /proc//ksm when loaded, sounds fine to me instead. If open of either one fails, application won't register in. It's up to you to choose KSM=M/N, if you want it as core functionality just build as KSM=Y but leave the option to others to save memory. -- 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