From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [PATCH/RFC] Shared page tables Date: Tue, 24 Jan 2006 08:18:27 +0100 References: <200601240210.04337.ak@suse.de> <1138086398.2977.19.camel@laptopd505.fenrus.org> In-Reply-To: <1138086398.2977.19.camel@laptopd505.fenrus.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200601240818.28696.ak@suse.de> Sender: owner-linux-mm@kvack.org Return-Path: To: Arjan van de Ven Cc: Ray Bryant , Dave McCracken , Robin Holt , Hugh Dickins , Linux Kernel , Linux Memory Management List-ID: On Tuesday 24 January 2006 08:06, Arjan van de Ven wrote: > > > The randomization is not for cache coloring, but for security purposes > > (except for the old very small stack randomization that was used > > to avoid conflicts on HyperThreaded CPUs). I would be surprised if the > > mmap made much difference because it's page aligned and at least > > on x86 the L2 and larger caches are usually PI. > > randomization to a large degree is more important between machines than > within the same machine (except for setuid stuff but lets call that a > special category for now). Imo prelink is one of the better bets to get > "all code for a binary/lib on the same 2 mb page", Probably yes. > all distros ship > prelink nowadays anyway SUSE doesn't use it. > (it's too much of a win that nobody can afford > to not ship it ;) KDE and some other people disagree on that. > and within prelink the balance between randomization > for security and 2Mb sharing can be struck best. In fact it needs know > about the 2Mb thing anyway to place it there properly and for all > binaries... the kernel just can't do that. Well, we first have to figure out if the shared page tables are really worth all the ugly code, nasty locking and other problems (inefficient TLB flush etc.) I personally would prefer to make large pages work better before going down that path. -Andi -- 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