From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 48F631A0325 for ; Fri, 29 Jan 2016 01:45:10 +1100 (AEDT) Received: from e23smtp09.au.ibm.com (e23smtp09.au.ibm.com [202.81.31.142]) (using TLSv1 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 1B382140BDE for ; Fri, 29 Jan 2016 01:45:10 +1100 (AEDT) Received: from localhost by e23smtp09.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 29 Jan 2016 00:45:08 +1000 Received: from d23relay08.au.ibm.com (d23relay08.au.ibm.com [9.185.71.33]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id 3EB193578052 for ; Fri, 29 Jan 2016 01:45:07 +1100 (EST) Received: from d23av02.au.ibm.com (d23av02.au.ibm.com [9.190.235.138]) by d23relay08.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u0SEiZMT48431222 for ; Fri, 29 Jan 2016 01:44:43 +1100 Received: from d23av02.au.ibm.com (localhost [127.0.0.1]) by d23av02.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u0SEiYXO027243 for ; Fri, 29 Jan 2016 01:44:34 +1100 From: "Aneesh Kumar K.V" To: Anshuman Khandual , linuxppc-dev@ozlabs.org Subject: Re: [PATCH 1/2] powerpc/mm: Enable HugeTLB page migration In-Reply-To: <1453972285-8822-1-git-send-email-khandual@linux.vnet.ibm.com> References: <1453972285-8822-1-git-send-email-khandual@linux.vnet.ibm.com> Date: Thu, 28 Jan 2016 20:14:15 +0530 Message-ID: <87io2dyda8.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Anshuman Khandual writes: > This enables HugeTLB page migration for PPC64_BOOK3S systems which implement > HugeTLB page at the PMD level. It enables the kernel configuration option > CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION by default which turns on the function > hugepage_migration_supported() during migration. After the recent changes > to the PTE format, HugeTLB page migration happens successfully. > > Signed-off-by: Anshuman Khandual > --- > arch/powerpc/Kconfig | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index e4824fd..65d52a0 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -82,6 +82,10 @@ config GENERIC_HWEIGHT > config ARCH_HAS_DMA_SET_COHERENT_MASK > bool > > +config ARCH_ENABLE_HUGEPAGE_MIGRATION > + def_bool y > + depends on PPC_BOOK3S_64 && HUGETLB_PAGE && MIGRATION > + > config PPC > bool > default y Are you sure this is all that is needed ? We will get a FOLL_GET with hugetlb migration and our follow_huge_addr will BUG_ON on that. Look at e66f17ff71772b209eed39de35aaa99ba819c93d (" mm/hugetlb: take page table lock in follow_huge_pmd()"). Again this doesn't work with 4K page size. So if you are taking this route, we will need that restriction here. I would suggest we switch 64K page size hugetlb to generic hugetlb and then do hugetlb migration on top of that. Till you help me understnd why that FOLL_GET issue is not valid for powerpc, NAK. -aneesh