Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755857AbYAYLmt (ORCPT ); Fri, 25 Jan 2008 06:42:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752789AbYAYLmj (ORCPT ); Fri, 25 Jan 2008 06:42:39 -0500 Received: from host36-195-149-62.serverdedicati.aruba.it ([62.149.195.36]:43895 "EHLO mx.cpushare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752631AbYAYLmi (ORCPT ); Fri, 25 Jan 2008 06:42:38 -0500 Date: Fri, 25 Jan 2008 12:42:29 +0100 From: Andrea Arcangeli To: Christoph Lameter Cc: Robin Holt , Avi Kivity , Izik Eidus , Nick Piggin , kvm-devel@lists.sourceforge.net, Benjamin Herrenschmidt , Peter Zijlstra , steiner@sgi.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, daniel.blueman@quadrics.com, Hugh Dickins Subject: Re: [patch 0/4] [RFC] MMU Notifiers V1 Message-ID: <20080125114229.GA7454@v2.random> References: <20080125055606.102986685@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080125055606.102986685@sgi.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3236 Lines: 70 On Thu, Jan 24, 2008 at 09:56:06PM -0800, Christoph Lameter wrote: > Andrea's mmu_notifier #4 -> RFC V1 > > - Merge subsystem rmap based with Linux rmap based approach > - Move Linux rmap based notifiers out of macro > - Try to account for what locks are held while the notifiers are > called. > - Develop a patch sequence that separates out the different types of > hooks so that it is easier to review their use. > - Avoid adding #include to linux/mm_types.h > - Integrate RCU logic suggested by Peter. I'm glad you're converging on something a bit saner and much much closer to my code, plus perfectly usable by KVM optimal rmap design too. It would have preferred if you would have sent me patches like Peter did for review and merging etc... that would have made review especially easier. Anyway I'm used to that on lkml so it's ok, I just need this patch to be included in mainline, everything else is irrelevant to me. On a technical merit this still partially makes me sick and I think it's the last issue to debate. @@ -971,6 +974,9 @@ int try_to_unmap(struct page *page, int else ret = try_to_unmap_file(page, migration); + if (unlikely(PageExternalRmap(page))) + mmu_rmap_notifier(invalidate_page, page); + if (!page_mapped(page)) ret = SWAP_SUCCESS; return ret; I find the above hard to accept, because the moment you work with physical pages and not "mm+address" I think you couldn't possibly care if page_mapped is true or false, and I think the above notifier should be called _outside_ try_to_unmap. Infact I'd call mmu_rmap_notifier(invalidate_page, page); only if page_unmapped is false and the linux pte is gone already (practically just before the page_count == 2 check and after try_to_unmap). I also think it's still worth to debate the rmap based on virtual or physical index. By supporting both secondary-rmap designs at the same time you seem to agree current KVM lightweight rmap implementation is a superior design at least for KVM. But by insisting on your rmap based on physical for your usage, you're implicitly telling us that is a superior design for you. But we know very little of why you can't exactly build rmap on virtual like KVM does! (especially now that you implicitly admitted KVM rmap design is superior at least for KVM it'd be interesting to know why you can't do the same exactly) You said something on that, but I certainly don't have a clear picture of why it can't work or why it would be less efficient. Like you said by PM I'd also like comments from Hugh, Nick and others about this issue. Nevertheless I'm very glad we already fully converged on the set_page_dirty, invalidate-page after ptep_clear_flush/young, etc... and furthermore that you only made very minor modification to my code to add a pair of hooks for the page-based rmap notifiers on top of my patch. So from a functionality POV this is 100% workable already from KVM side! Thanks! -- 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/