From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id DFA0F6B000A for ; Mon, 9 Jul 2018 01:40:50 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id g20-v6so11058346pfi.2 for ; Sun, 08 Jul 2018 22:40:50 -0700 (PDT) Received: from mga12.intel.com (mga12.intel.com. [192.55.52.136]) by mx.google.com with ESMTPS id z3-v6si13486914pgl.579.2018.07.08.22.40.49 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 08 Jul 2018 22:40:49 -0700 (PDT) From: "Huang\, Ying" Subject: Re: [PATCH -mm -v4 01/21] mm, THP, swap: Enable PMD swap operations for CONFIG_THP_SWAP References: <20180622035151.6676-1-ying.huang@intel.com> <20180622035151.6676-2-ying.huang@intel.com> Date: Mon, 09 Jul 2018 13:40:45 +0800 In-Reply-To: (Dan Williams's message of "Sat, 7 Jul 2018 14:11:18 -0700") Message-ID: <87muv1kluq.fsf@yhuang-dev.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams Cc: Andrew Morton , linux-mm , Linux Kernel Mailing List , "Kirill A. Shutemov" , Andrea Arcangeli , Michal Hocko , Johannes Weiner , Shaohua Li , hughd@google.com, Minchan Kim , Rik van Riel , Dave Hansen , n-horiguchi@ah.jp.nec.com, zi.yan@cs.rutgers.edu, daniel.m.jordan@oracle.com 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. Best Regards, Huang, Ying