From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot1-f72.google.com (mail-ot1-f72.google.com [209.85.210.72]) by kanga.kvack.org (Postfix) with ESMTP id 3D2A56B0003 for ; Wed, 10 Oct 2018 23:17:03 -0400 (EDT) Received: by mail-ot1-f72.google.com with SMTP id j65-v6so5269960otc.5 for ; Wed, 10 Oct 2018 20:17:03 -0700 (PDT) Received: from foss.arm.com (usa-sjc-mx-foss1.foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id d15si9688402oti.61.2018.10.10.20.17.01 for ; Wed, 10 Oct 2018 20:17:01 -0700 (PDT) Subject: Re: [PATCH 1/4] mm/hugetlb: Enable PUD level huge page migration References: <20181003065833.GD18290@dhcp22.suse.cz> <7f0488b5-053f-0954-9b95-8c0890ef5597@arm.com> <20181003105926.GA4714@dhcp22.suse.cz> <34b25855-fcef-61ed-312d-2011f80bdec4@arm.com> <20181003114842.GD4714@dhcp22.suse.cz> <20181003133609.GG4714@dhcp22.suse.cz> <5dc1dc4d-de60-43b9-aab6-3b3bb6a22a4b@arm.com> <20181009141442.GT8528@dhcp22.suse.cz> <20181010093907.GF5873@dhcp22.suse.cz> From: Anshuman Khandual Message-ID: <4127aad2-e8f4-3fcf-ffe3-7a23147885ce@arm.com> Date: Thu, 11 Oct 2018 08:46:55 +0530 MIME-Version: 1.0 In-Reply-To: <20181010093907.GF5873@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, suzuki.poulose@arm.com, punit.agrawal@arm.com, will.deacon@arm.com, Steven.Price@arm.com, catalin.marinas@arm.com, mike.kravetz@oracle.com, n-horiguchi@ah.jp.nec.com On 10/10/2018 03:09 PM, Michal Hocko wrote: > On Wed 10-10-18 08:39:22, Anshuman Khandual wrote: > [...] >> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h >> index 9df1d59..4bcbf1e 100644 >> --- a/include/linux/hugetlb.h >> +++ b/include/linux/hugetlb.h >> @@ -504,6 +504,16 @@ static inline bool hugepage_migration_supported(struct hstate *h) >> return arch_hugetlb_migration_supported(h); >> } >> >> +static inline bool hugepage_movable_supported(struct hstate *h) >> +{ >> + if (!hugepage_migration_supported(h)) --> calls arch override restricting the set >> + return false; >> + >> + if (hstate_is_gigantic(h) --------> restricts the set further >> + return false; >> + return true; >> +} >> + >> static inline spinlock_t *huge_pte_lockptr(struct hstate *h, >> struct mm_struct *mm, pte_t *pte) >> { >> @@ -600,6 +610,11 @@ static inline bool hugepage_migration_supported(struct hstate *h) >> return false; >> } >> >> +static inline bool hugepage_movable_supported(struct hstate *h) >> +{ >> + return false; >> +} >> + >> static inline spinlock_t *huge_pte_lockptr(struct hstate *h, >> struct mm_struct *mm, pte_t *pte) >> { >> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >> index 3c21775..a5a111d 100644 >> --- a/mm/hugetlb.c >> +++ b/mm/hugetlb.c >> @@ -919,7 +919,7 @@ static struct page *dequeue_huge_page_nodemask(struct hstate *h, gfp_t gfp_mask, >> /* Movability of hugepages depends on migration support. */ >> static inline gfp_t htlb_alloc_mask(struct hstate *h) >> { >> - if (hugepage_migration_supported(h)) >> + if (hugepage_movable_supported(h)) >> return GFP_HIGHUSER_MOVABLE; >> else >> return GFP_HIGHUSER; > > Exactly what I've had in mind. It would be great to have a comment in > hugepage_movable_supported to explain why we are not supporting giga > pages even though they are migrateable and why we need that distinction. sure, will do. > >> The above patch is in addition to the following later patch in the series. > [...] >> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h >> index 9c1b77f..9df1d59 100644 >> --- a/include/linux/hugetlb.h >> +++ b/include/linux/hugetlb.h >> @@ -479,18 +479,29 @@ static inline pgoff_t basepage_index(struct page *page) >> extern int dissolve_free_huge_page(struct page *page); >> extern int dissolve_free_huge_pages(unsigned long start_pfn, >> unsigned long end_pfn); >> -static inline bool hugepage_migration_supported(struct hstate *h) >> -{ >> + >> #ifdef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION >> +#ifndef arch_hugetlb_migration_supported >> +static inline bool arch_hugetlb_migration_supported(struct hstate *h) >> +{ >> if ((huge_page_shift(h) == PMD_SHIFT) || >> (huge_page_shift(h) == PUD_SHIFT) || >> (huge_page_shift(h) == PGDIR_SHIFT)) >> return true; >> else >> return false; >> +} >> +#endif >> #else >> +static inline bool arch_hugetlb_migration_supported(struct hstate *h) >> +{ >> return false; >> +} >> #endif >> + >> +static inline bool hugepage_migration_supported(struct hstate *h) >> +{ >> + return arch_hugetlb_migration_supported(h); >> } > > Yes making hugepage_migration_supported to have an arch override is > definitely the right thing to do. Whether the above approach rather than > a weak symbol is better is a matter of taste and I do not feel strongly > about that. Okay then, will carry this forward and re-spin the patch series. Thank you for your detailed review till now.