Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755295AbdGKGuk convert rfc822-to-8bit (ORCPT ); Tue, 11 Jul 2017 02:50:40 -0400 Received: from tyo161.gate.nec.co.jp ([114.179.232.161]:55987 "EHLO tyo161.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752170AbdGKGuh (ORCPT ); Tue, 11 Jul 2017 02:50:37 -0400 From: Naoya Horiguchi To: Zi Yan CC: "kirill.shutemov@linux.intel.com" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "akpm@linux-foundation.org" , "minchan@kernel.org" , "vbabka@suse.cz" , "mgorman@techsingularity.net" , "mhocko@kernel.org" , "khandual@linux.vnet.ibm.com" , "zi.yan@cs.rutgers.edu" , "dnellans@nvidia.com" , "dave.hansen@intel.com" Subject: Re: [PATCH v8 05/10] mm: thp: enable thp migration in generic path Thread-Topic: [PATCH v8 05/10] mm: thp: enable thp migration in generic path Thread-Index: AQHS+hGV5znhtdAGSEOzBurWcUhu6A== Date: Tue, 11 Jul 2017 06:47:37 +0000 Message-ID: <20170711064736.GB22052@hori1.linux.bs1.fc.nec.co.jp> References: <20170701134008.110579-1-zi.yan@sent.com> <20170701134008.110579-6-zi.yan@sent.com> In-Reply-To: <20170701134008.110579-6-zi.yan@sent.com> Accept-Language: en-US, ja-JP Content-Language: ja-JP X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.128.101.17] Content-Type: text/plain; charset="iso-2022-jp" Content-ID: Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-TM-AS-MML: disable Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4312 Lines: 117 On Sat, Jul 01, 2017 at 09:40:03AM -0400, Zi Yan wrote: > From: Zi Yan > > This patch adds thp migration's core code, including conversions > between a PMD entry and a swap entry, setting PMD migration entry, > removing PMD migration entry, and waiting on PMD migration entries. > > This patch makes it possible to support thp migration. > If you fail to allocate a destination page as a thp, you just split > the source thp as we do now, and then enter the normal page migration. > If you succeed to allocate destination thp, you enter thp migration. > Subsequent patches actually enable thp migration for each caller of > page migration by allowing its get_new_page() callback to > allocate thps. > > ChangeLog v1 -> v2: > - support pte-mapped thp, doubly-mapped thp > > Signed-off-by: Naoya Horiguchi > > ChangeLog v2 -> v3: > - use page_vma_mapped_walk() > - use pmdp_huge_clear_flush() instead of pmdp_huge_get_and_clear() in > set_pmd_migration_entry() > > ChangeLog v3 -> v4: > - factor out the code of removing pte pgtable page in zap_huge_pmd() > > ChangeLog v4 -> v5: > - remove unnecessary PTE-mapped THP code in remove_migration_pmd() > and set_pmd_migration_entry() > - restructure the code in zap_huge_pmd() to avoid factoring out > the pte pgtable page code > - in zap_huge_pmd(), check that PMD swap entries are migration entries > - change author information > > ChangeLog v5 -> v7 > - use macro to disable the code when thp migration is not enabled > > ChangeLog v7 -> v8 > - use IS_ENABLED instead of macro to make code look clean in > zap_huge_pmd() and page_vma_mapped_walk() > - remove BUILD_BUG() in pmd_to_swp_entry() and swp_entry_to_pmd() to > avoid compilation error > - rename variable 'migration' to 'flush_needed' and invert the logic in > zap_huge_pmd() to make code more descriptive > - use pmdp_invalidate() in set_pmd_migration_entry() to avoid race > with MADV_DONTNEED > - remove unnecessary tlb flush in remove_migration_pmd() > - add the missing migration flag check in page_vma_mapped_walk() > > Signed-off-by: Zi Yan > Cc: Kirill A. Shutemov > --- > arch/x86/include/asm/pgtable_64.h | 2 + > include/linux/swapops.h | 67 ++++++++++++++++++++++++++++++- > mm/huge_memory.c | 84 ++++++++++++++++++++++++++++++++++++--- > mm/migrate.c | 32 ++++++++++++++- > mm/page_vma_mapped.c | 18 +++++++-- > mm/pgtable-generic.c | 3 +- > mm/rmap.c | 13 ++++++ > 7 files changed, 207 insertions(+), 12 deletions(-) > ... > diff --git a/mm/rmap.c b/mm/rmap.c > index 91948fbbb0bb..b28f633cd569 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1302,6 +1302,7 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, > bool ret = true; > enum ttu_flags flags = (enum ttu_flags)arg; > > + > /* munlock has nothing to gain from examining un-locked vmas */ > if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED)) > return true; > @@ -1312,6 +1313,18 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, > } > > while (page_vma_mapped_walk(&pvmw)) { > +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION > + /* PMD-mapped THP migration entry */ > + if (flags & TTU_MIGRATION) { My testing based on mmotm-2017-07-06-16-18 showed that migrating shmem thp caused kernel crash. I don't think this is critical because that case is just not-prepared yet. So in order to avoid the crash, please add PageAnon(page) check here. This makes shmem thp migration just fail. + if (!PageAnon(page)) + continue; > + if (!pvmw.pte && page) { Just from curiosity, do we really need this page check? try_to_unmap() always passes down the parameter 'page' to try_to_unmap_one() via rmap_walk_* family, so I think we can assume page is always non-NULL. Thanks, Naoya Horiguchi > + VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), > + page); > + set_pmd_migration_entry(&pvmw, page); > + continue; > + } > + } > +#endif > + > /* > * If the page is mlock()d, we cannot swap it out. > * If it's recently referenced (perhaps page_referenced > -- > 2.11.0 > >