From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E8CDC4332F for ; Thu, 23 Sep 2021 22:24:13 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B763A60F56 for ; Thu, 23 Sep 2021 22:24:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org B763A60F56 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 2BD77940008; Thu, 23 Sep 2021 18:24:12 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 21F1F6B0071; Thu, 23 Sep 2021 18:24:12 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 10DF8940008; Thu, 23 Sep 2021 18:24:12 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0206.hostedemail.com [216.40.44.206]) by kanga.kvack.org (Postfix) with ESMTP id 024A96B006C for ; Thu, 23 Sep 2021 18:24:12 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id B4BC98249980 for ; Thu, 23 Sep 2021 22:24:11 +0000 (UTC) X-FDA: 78620267502.01.DBF01A2 Received: from mail-ed1-f44.google.com (mail-ed1-f44.google.com [209.85.208.44]) by imf22.hostedemail.com (Postfix) with ESMTP id 76BAB1904 for ; Thu, 23 Sep 2021 22:24:11 +0000 (UTC) Received: by mail-ed1-f44.google.com with SMTP id dj4so28665773edb.5 for ; Thu, 23 Sep 2021 15:24:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=CT7KCr5JzmhOzp1OYQQLzyUDx7iSATgAJPZ9wyLVnkI=; b=o5Xnf0ITeHNqTJoBcm0mowoAq7IDRRWUgZ+GRG1+fnouy0GcArivFUNZ9VpEQsELNl kI3oBEw1GqVfZbjuGr4REvG94qEn59tl9me/BuAZ5dlO4b96KbRT0euPgCEuF/oajemB BasmLrZJWcDc3tHgkzhssHOVk2SCZpaCBMoO6znTgP0uT5Cl0AZxxSBEFN8WpvFn+qJJ GSeVSeWWegawuQFt7uQcpEWgSWUjyEo4fRDxYxFYXXB6KwoeoFR1q/0F6B5sEHbfi4RT Tp/irL1+6RCTSC1dlCIKcEj/u4n7oAyGFoqBthPcIWZwTuZccMcItdQA5gOTGm1/4oQc idDQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=CT7KCr5JzmhOzp1OYQQLzyUDx7iSATgAJPZ9wyLVnkI=; b=xFIbiBrthtj4a9cCPRpif91xwejamC7OxjsFM0ES4pMEFUmMljA6vz8l68DkaqhhfJ bJ4g+tcLHPD1MKvvUqPeLGnIAxQuZNofB+U9gGDBdf+z9h/nJiq8FYahY3uhXiL91S5w 4pYuthB/BrstKZayEVBFqUBZs/Acj7GtA1lY4qHyHFakfmYwvXB1iiNrs+s0VGSii0xW +qXED2i2E2knytmaNB6yXpTP0HKqozRn4NoIaYDJtjZteS4DWDqQ3R/H5TXzyRMRsvUW 56Iz8ZjRhXhIoqvdix46pPpCnaUPdjelq2Q5N6X9iC1bqPjF/EFKolCYXqSCjQni/xaK aRag== X-Gm-Message-State: AOAM531xst86CK9K8JkHPqc93IFt97ezXCLJMOml1IG830uPUPNyNwWW VkKHsJ1nZd/PWrS7XbXF5tkGxL9LsVJJgCjGWsE= X-Google-Smtp-Source: ABdhPJw+DXDQzdLXxBE3qxnoYiooEh2Ka+AByTiMPKUDWPoJ1ePyYaBK83sIryPyIHDdOKP4GqFNUMmE/bLFXmifTKU= X-Received: by 2002:a50:cd87:: with SMTP id p7mr1547322edi.294.1632435850397; Thu, 23 Sep 2021 15:24:10 -0700 (PDT) MIME-Version: 1.0 References: <20210922102411.34494-1-songmuchun@bytedance.com> <20210922102411.34494-3-songmuchun@bytedance.com> In-Reply-To: <20210922102411.34494-3-songmuchun@bytedance.com> From: Barry Song <21cnbao@gmail.com> Date: Fri, 24 Sep 2021 10:23:59 +1200 Message-ID: Subject: Re: [PATCH v3 2/4] mm: hugetlb: replace hugetlb_free_vmemmap_enabled with a static_key To: Muchun Song Cc: Mike Kravetz , Andrew Morton , Oscar Salvador , Michal Hocko , Barry Song , David Hildenbrand , Chen Huang , "Bodeddula, Balasubramaniam" , Jonathan Corbet , Matthew Wilcox , Xiongchun duan , fam.zheng@bytedance.com, Muchun Song , Qi Zheng , linux-doc@vger.kernel.org, LKML , Linux-MM Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=o5Xnf0IT; spf=pass (imf22.hostedemail.com: domain of 21cnbao@gmail.com designates 209.85.208.44 as permitted sender) smtp.mailfrom=21cnbao@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 76BAB1904 X-Stat-Signature: rcq5it3t4rzyfoc6d66ieyp4r17m8h8s X-HE-Tag: 1632435851-606017 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Sep 22, 2021 at 10:27 PM Muchun Song wrote: > > The page_head_if_fake() is used throughout memory management and the > conditional check requires checking a global variable, although the > overhead of this check may be small, it increases when the memory > cache comes under pressure. Also, the global variable will not be > modified after system boot, so it is very appropriate to use static > key machanism. > > Signed-off-by: Muchun Song > --- > include/linux/hugetlb.h | 10 ++++++++-- > include/linux/page-flags.h | 6 ++++-- > mm/hugetlb_vmemmap.c | 12 ++++++------ > mm/memory_hotplug.c | 2 +- > 4 files changed, 19 insertions(+), 11 deletions(-) > > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index 1faebe1cd0ed..4cc647a5dbf8 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -1066,9 +1066,15 @@ static inline void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr > #endif /* CONFIG_HUGETLB_PAGE */ > > #ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP > -extern bool hugetlb_free_vmemmap_enabled; > +static inline bool hugetlb_free_vmemmap_enabled(void) > +{ > + return static_key_enabled(&hugetlb_free_vmemmap_enabled_key); could it be if (static_branch_maybe(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON, &hugetlb_free_vmemmap_enabled_key)) then we are able to remove the duplication in page_fixed_fake_head()? > +} > #else > -#define hugetlb_free_vmemmap_enabled false > +static inline bool hugetlb_free_vmemmap_enabled(void) > +{ > + return false; > +} > #endif > > static inline spinlock_t *huge_pte_lock(struct hstate *h, > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index b47a7f51d2c3..54e119e44496 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -185,7 +185,8 @@ enum pageflags { > #ifndef __GENERATING_BOUNDS_H > > #ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP > -extern bool hugetlb_free_vmemmap_enabled; > +DECLARE_STATIC_KEY_MAYBE(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON, > + hugetlb_free_vmemmap_enabled_key); > > /* > * If the feature of freeing some vmemmap pages associated with each HugeTLB > @@ -205,7 +206,8 @@ extern bool hugetlb_free_vmemmap_enabled; > */ > static __always_inline const struct page *page_fixed_fake_head(const struct page *page) > { > - if (!hugetlb_free_vmemmap_enabled) > + if (!static_branch_maybe(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON, > + &hugetlb_free_vmemmap_enabled_key)) > return page; > /* > * Only addresses aligned with PAGE_SIZE of struct page may be fake head > diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c > index 527bcaa44a48..47517e878ed5 100644 > --- a/mm/hugetlb_vmemmap.c > +++ b/mm/hugetlb_vmemmap.c > @@ -188,9 +188,9 @@ > #define RESERVE_VMEMMAP_NR 1U > #define RESERVE_VMEMMAP_SIZE (RESERVE_VMEMMAP_NR << PAGE_SHIFT) > > -bool hugetlb_free_vmemmap_enabled __read_mostly = > - IS_ENABLED(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON); > -EXPORT_SYMBOL(hugetlb_free_vmemmap_enabled); > +DEFINE_STATIC_KEY_MAYBE(CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON, > + hugetlb_free_vmemmap_enabled_key); > +EXPORT_SYMBOL(hugetlb_free_vmemmap_enabled_key); > > static int __init early_hugetlb_free_vmemmap_param(char *buf) > { > @@ -204,9 +204,9 @@ static int __init early_hugetlb_free_vmemmap_param(char *buf) > return -EINVAL; > > if (!strcmp(buf, "on")) > - hugetlb_free_vmemmap_enabled = true; > + static_branch_enable(&hugetlb_free_vmemmap_enabled_key); > else if (!strcmp(buf, "off")) > - hugetlb_free_vmemmap_enabled = false; > + static_branch_disable(&hugetlb_free_vmemmap_enabled_key); > else > return -EINVAL; > > @@ -284,7 +284,7 @@ void __init hugetlb_vmemmap_init(struct hstate *h) > BUILD_BUG_ON(__NR_USED_SUBPAGE >= > RESERVE_VMEMMAP_SIZE / sizeof(struct page)); > > - if (!hugetlb_free_vmemmap_enabled) > + if (!hugetlb_free_vmemmap_enabled()) > return; > > vmemmap_pages = (nr_pages * sizeof(struct page)) >> PAGE_SHIFT; > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 0488eed3327c..89c1fde02162 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1341,7 +1341,7 @@ bool mhp_supports_memmap_on_memory(unsigned long size) > * populate a single PMD. > */ > return memmap_on_memory && > - !hugetlb_free_vmemmap_enabled && > + !hugetlb_free_vmemmap_enabled() && > IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) && > size == memory_block_size_bytes() && > IS_ALIGNED(vmemmap_size, PMD_SIZE) && > -- > 2.11.0 > Thanks barry