From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f69.google.com (mail-oi0-f69.google.com [209.85.218.69]) by kanga.kvack.org (Postfix) with ESMTP id 22AB76B0269 for ; Mon, 9 Jul 2018 02:08:26 -0400 (EDT) Received: by mail-oi0-f69.google.com with SMTP id b8-v6so13796148oib.4 for ; Sun, 08 Jul 2018 23:08:26 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id i3-v6sor9459513oia.184.2018.07.08.23.08.25 for (Google Transport Security); Sun, 08 Jul 2018 23:08:25 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <87muv1kluq.fsf@yhuang-dev.intel.com> References: <20180622035151.6676-1-ying.huang@intel.com> <20180622035151.6676-2-ying.huang@intel.com> <87muv1kluq.fsf@yhuang-dev.intel.com> From: Dan Williams Date: Sun, 8 Jul 2018 23:08:24 -0700 Message-ID: Subject: Re: [PATCH -mm -v4 01/21] mm, THP, swap: Enable PMD swap operations for CONFIG_THP_SWAP Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: "Huang, Ying" Cc: Andrew Morton , linux-mm , Linux Kernel Mailing List , "Kirill A. Shutemov" , Andrea Arcangeli , Michal Hocko , Johannes Weiner , Shaohua Li , Hugh Dickins , Minchan Kim , Rik van Riel , Dave Hansen , Naoya Horiguchi , zi.yan@cs.rutgers.edu, daniel.m.jordan@oracle.com On Sun, Jul 8, 2018 at 10:40 PM, Huang, Ying wrote: > Dan Williams writes: > >> On Thu, Jun 21, 2018 at 8:55 PM Huang, Ying wrote: >>> >>> From: Huang Ying >>> >>> Previously, the PMD swap operations are only enabled for >>> CONFIG_ARCH_ENABLE_THP_MIGRATION. Because they are only used by the >>> THP migration support. We will support PMD swap mapping to the huge >>> swap cluster and swapin the THP as a whole. That will be enabled via >>> CONFIG_THP_SWAP and needs these PMD swap operations. So enable the >>> PMD swap operations for CONFIG_THP_SWAP too. >>> >>> Signed-off-by: "Huang, Ying" >>> Cc: "Kirill A. Shutemov" >>> Cc: Andrea Arcangeli >>> Cc: Michal Hocko >>> Cc: Johannes Weiner >>> Cc: Shaohua Li >>> Cc: Hugh Dickins >>> Cc: Minchan Kim >>> Cc: Rik van Riel >>> Cc: Dave Hansen >>> Cc: Naoya Horiguchi >>> Cc: Zi Yan >>> Cc: Daniel Jordan >>> --- >>> arch/x86/include/asm/pgtable.h | 2 +- >>> include/asm-generic/pgtable.h | 2 +- >>> include/linux/swapops.h | 44 ++++++++++++++++++++++-------------------- >>> 3 files changed, 25 insertions(+), 23 deletions(-) >>> >>> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h >>> index 99ecde23c3ec..13bf58838daf 100644 >>> --- a/arch/x86/include/asm/pgtable.h >>> +++ b/arch/x86/include/asm/pgtable.h >>> @@ -1224,7 +1224,7 @@ static inline pte_t pte_swp_clear_soft_dirty(pte_t pte) >>> return pte_clear_flags(pte, _PAGE_SWP_SOFT_DIRTY); >>> } >>> >>> -#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION >>> +#if defined(CONFIG_ARCH_ENABLE_THP_MIGRATION) || defined(CONFIG_THP_SWAP) >> >> How about introducing a new config symbol representing the common >> infrastructure between the two and have them select that symbol. > > The common infrastructure shared by two mechanisms is PMD swap entry. > But I didn't find there are many places where the common infrastructure > is used. So I think it may be over-engineering to introduce a new > config symbol but use it for so few times. > >> Would that also allow us to clean up the usage of >> CONFIG_ARCH_ENABLE_THP_MIGRATION in fs/proc/task_mmu.c? In other >> words, what's the point of having nice ifdef'd alternatives in header >> files when ifdefs are still showing up in C files, all of it should be >> optionally determined by header files. > > Unfortunately, I think it is not a easy task to wrap all C code via > #ifdef in header files. And it may be over-engineering to wrap them > all. I guess this is why there are still some #ifdef in C files. That's the entire point. Yes, over-engineer the header files so the actual C code is more readable.