From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Ray Bryant" Subject: Re: [PATCH/RFC] Shared page tables Date: Mon, 23 Jan 2006 18:53:54 -0600 References: <200601231816.38942.raybry@mpdtxmail.amd.com> <200601240139.46751.ak@suse.de> In-Reply-To: <200601240139.46751.ak@suse.de> MIME-Version: 1.0 Message-ID: <200601231853.54948.raybry@mpdtxmail.amd.com> Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: owner-linux-mm@kvack.org Return-Path: To: Andi Kleen Cc: Dave McCracken , Robin Holt , Hugh Dickins , Linux Kernel , Linux Memory Management List-ID: On Monday 23 January 2006 18:39, Andi Kleen wrote: > On Tuesday 24 January 2006 01:16, Ray Bryant wrote: > > On Monday 23 January 2006 17:58, Ray Bryant wrote: > > > > > > > ... And what kind of alignment constraints do we end up > > > under in order to make the sharing happen? (My guess would be that > > > there aren't any such constraints (well, page alignment.. :-) if we > > > are just sharing pte's.) > > > > Oh, obviously that is not right as you have to share full pte pages. So > > on x86_64 I'm guessing one needs 2MB alignment in order to get the > > sharing to kick in, since a pte page maps 512 pages of 4 KB each. > > The new randomized mmaps will likely actively sabotate such alignment. I > just added them for x86-64. > > -Andi Hmmm, does that mean there is a fundamental conflict between the desire to share pte's and getting good cache coloring behavior? Isn't it the case that if the region is large enough (say >> 2MB), that randomized mmaps will just cause the first partial page of pte's to not be shareable, and as soon as we have a full pte page mapped into the file that the full pte pages will be shareable, etc, until the last (partial) pte page is not shareable? > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Ray Bryant AMD Performance Labs Austin, Tx 512-602-0038 (o) 512-507-7807 (c) -- 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