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Sat, 25 Sep 2021 20:15:00 -0700 (PDT) Received: from localhost.localdomain ([61.120.150.70]) by smtp.gmail.com with ESMTPSA id v26sm13374862pfm.175.2021.09.25.20.14.53 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 25 Sep 2021 20:15:00 -0700 (PDT) From: Muchun Song To: mike.kravetz@oracle.com, akpm@linux-foundation.org, osalvador@suse.de, mhocko@suse.com, song.bao.hua@hisilicon.com, david@redhat.com, chenhuang5@huawei.com, bodeddub@amazon.com, corbet@lwn.net, willy@infradead.org, 21cnbao@gmail.com Cc: duanxiongchun@bytedance.com, fam.zheng@bytedance.com, smuchun@gmail.com, zhengqi.arch@bytedance.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Muchun Song Subject: [PATCH v4 2/5] mm: hugetlb: replace hugetlb_free_vmemmap_enabled with a static_key Date: Sun, 26 Sep 2021 11:13:36 +0800 Message-Id: <20210926031339.40043-3-songmuchun@bytedance.com> X-Mailer: git-send-email 2.21.0 (Apple Git-122) In-Reply-To: <20210926031339.40043-1-songmuchun@bytedance.com> References: <20210926031339.40043-1-songmuchun@bytedance.com> MIME-Version: 1.0 X-Rspamd-Queue-Id: 93DE9900013E X-Stat-Signature: szmkagtshgxdpxdwp9u8qs6ysatg4gpu Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=bytedance-com.20210112.gappssmtp.com header.s=20210112 header.b=nqbT0e8T; spf=pass (imf29.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.214.175 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com; dmarc=pass (policy=none) header.from=bytedance.com X-Rspamd-Server: rspam06 X-HE-Tag: 1632626101-4084 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: 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 Reviewed-by: Barry Song --- include/linux/hugetlb.h | 6 ------ include/linux/page-flags.h | 18 +++++++++++++++--- mm/hugetlb_vmemmap.c | 12 ++++++------ mm/memory_hotplug.c | 2 +- 4 files changed, 22 insertions(+), 16 deletions(-) diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 3cbf60464398..a90cc88195da 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -1055,12 +1055,6 @@ 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; -#else -#define hugetlb_free_vmemmap_enabled false -#endif - static inline spinlock_t *huge_pte_lock(struct hstate *h, struct mm_struct *mm, pte_t *pte) { diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index b49808e748ce..26e540fd3393 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -185,7 +185,14 @@ 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); + +static __always_inline bool hugetlb_free_vmemmap_enabled(void) +{ + return static_branch_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 +212,7 @@ 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 (!hugetlb_free_vmemmap_enabled()) return page; /* @@ -229,10 +236,15 @@ static __always_inline const struct page *page_fixed_fake_head(const struct page return page; } #else -static __always_inline const struct page *page_fixed_fake_head(const struct page *page) +static inline const struct page *page_fixed_fake_head(const struct page *page) { return page; } + +static inline bool hugetlb_free_vmemmap_enabled(void) +{ + return false; +} #endif static __always_inline int page_is_fake_head(struct page *page) diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c index f4a8fca691ee..22ecb5e21686 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 4ea91c3ff768..66eaa4e2e76f 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) &&