From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Subject: Re: [PATCH v2 1/3] arm64: mm: use appropriate ctors for page tables Date: Tue, 19 Feb 2019 17:34:07 -0800 Message-ID: <20190220013407.GD12668@bombadil.infradead.org> References: <20190214211642.2200-1-yuzhao@google.com> <20190218231319.178224-1-yuzhao@google.com> <863acc9a-53fb-86ad-4521-828ee8d9c222@arm.com> <20190219053205.GA124985@google.com> <8f9b0bfb-b787-fa3e-7322-73a56a618aa8@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <8f9b0bfb-b787-fa3e-7322-73a56a618aa8@arm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Anshuman Khandual Cc: Mark Rutland , linux-arch@vger.kernel.org, Yu Zhao , Ard Biesheuvel , Peter Zijlstra , Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org, Nick Piggin , Jun Yao , linux-mm@kvack.org, "Aneesh Kumar K . V" , Chintan Pandya , Joel Fernandes , "Kirill A . Shutemov" , Andrew Morton , Laura Abbott , linux-arm-kernel@lists.infradead.org List-Id: linux-arch.vger.kernel.org On Tue, Feb 19, 2019 at 11:47:12AM +0530, Anshuman Khandual wrote: > + Matthew Wilcox > On 02/19/2019 11:02 AM, Yu Zhao wrote: > > On Tue, Feb 19, 2019 at 09:51:01AM +0530, Anshuman Khandual wrote: > >> > >> > >> On 02/19/2019 04:43 AM, Yu Zhao wrote: > >>> For pte page, use pgtable_page_ctor(); for pmd page, use > >>> pgtable_pmd_page_ctor() if not folded; and for the rest (pud, > >>> p4d and pgd), don't use any. > >> pgtable_page_ctor()/dtor() is not optional for any level page table page > >> as it determines the struct page state and zone statistics. > > > > This is not true. pgtable_page_ctor() is only meant for user pte > > page. The name isn't perfect (we named it this way before we had > > split pmd page table lock, and never bothered to change it). > > > > The commit cccd843f54be ("mm: mark pages in use for page tables") Where did you get that commit ID from? In Linus' tree, it's 1d40a5ea01d53251c23c7be541d3f4a656cfc537 > > clearly states so: > > Note that only pages currently accounted as NR_PAGETABLES are > > tracked as PageTable; this does not include pgd/p4d/pud/pmd pages. > > I think the commit is the following one and it does say so. But what is > the rationale of tagging only PTE page as PageTable and updating the zone > stat but not doing so for higher level page table pages ? Are not they > used as page table pages ? Should not they count towards NR_PAGETABLE ? > > 1d40a5ea01d53251c ("mm: mark pages in use for page tables") I think they should all be accounted towards NR_PAGETABLE and marked as being PageTable. Somebody needs to make the case for that and send the patches. That patch even says that there should be follow-up patches to do that. I've been a little busy and haven't got back to it. I thought you said you were going to do it. > pgtable_page_ctor/dtor() use across arch is not consistent and there is a need > for generalization which has been already acknowledged earlier. But for now we > can atleast fix this on arm64. > > https://lore.kernel.org/lkml/1547619692-7946-1-git-send-email-anshuman.khandual@arm.com/ ... were you not listening when you were told that was completely inadequate? From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org ([198.137.202.133]:44848 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725616AbfBTBeP (ORCPT ); Tue, 19 Feb 2019 20:34:15 -0500 Date: Tue, 19 Feb 2019 17:34:07 -0800 From: Matthew Wilcox Subject: Re: [PATCH v2 1/3] arm64: mm: use appropriate ctors for page tables Message-ID: <20190220013407.GD12668@bombadil.infradead.org> References: <20190214211642.2200-1-yuzhao@google.com> <20190218231319.178224-1-yuzhao@google.com> <863acc9a-53fb-86ad-4521-828ee8d9c222@arm.com> <20190219053205.GA124985@google.com> <8f9b0bfb-b787-fa3e-7322-73a56a618aa8@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8f9b0bfb-b787-fa3e-7322-73a56a618aa8@arm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Anshuman Khandual Cc: Yu Zhao , Catalin Marinas , Will Deacon , "Aneesh Kumar K . V" , Andrew Morton , Nick Piggin , Peter Zijlstra , Joel Fernandes , "Kirill A . Shutemov" , Mark Rutland , Ard Biesheuvel , Chintan Pandya , Jun Yao , Laura Abbott , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org Message-ID: <20190220013407.iZrJeluxSZwSKeMo7KUqRNKzFze1QCx1GimF_0dNsXw@z> On Tue, Feb 19, 2019 at 11:47:12AM +0530, Anshuman Khandual wrote: > + Matthew Wilcox > On 02/19/2019 11:02 AM, Yu Zhao wrote: > > On Tue, Feb 19, 2019 at 09:51:01AM +0530, Anshuman Khandual wrote: > >> > >> > >> On 02/19/2019 04:43 AM, Yu Zhao wrote: > >>> For pte page, use pgtable_page_ctor(); for pmd page, use > >>> pgtable_pmd_page_ctor() if not folded; and for the rest (pud, > >>> p4d and pgd), don't use any. > >> pgtable_page_ctor()/dtor() is not optional for any level page table page > >> as it determines the struct page state and zone statistics. > > > > This is not true. pgtable_page_ctor() is only meant for user pte > > page. The name isn't perfect (we named it this way before we had > > split pmd page table lock, and never bothered to change it). > > > > The commit cccd843f54be ("mm: mark pages in use for page tables") Where did you get that commit ID from? In Linus' tree, it's 1d40a5ea01d53251c23c7be541d3f4a656cfc537 > > clearly states so: > > Note that only pages currently accounted as NR_PAGETABLES are > > tracked as PageTable; this does not include pgd/p4d/pud/pmd pages. > > I think the commit is the following one and it does say so. But what is > the rationale of tagging only PTE page as PageTable and updating the zone > stat but not doing so for higher level page table pages ? Are not they > used as page table pages ? Should not they count towards NR_PAGETABLE ? > > 1d40a5ea01d53251c ("mm: mark pages in use for page tables") I think they should all be accounted towards NR_PAGETABLE and marked as being PageTable. Somebody needs to make the case for that and send the patches. That patch even says that there should be follow-up patches to do that. I've been a little busy and haven't got back to it. I thought you said you were going to do it. > pgtable_page_ctor/dtor() use across arch is not consistent and there is a need > for generalization which has been already acknowledged earlier. But for now we > can atleast fix this on arm64. > > https://lore.kernel.org/lkml/1547619692-7946-1-git-send-email-anshuman.khandual@arm.com/ ... were you not listening when you were told that was completely inadequate?