linux-kernel - [RFC PATCH 03/24] mm/hugetlb: Introduce a new config HUGETLB_PAGE_FREE

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Message-Id: <20200915125947.26204-4-songmuchun@bytedance.com>
Date:   Tue, 15 Sep 2020 20:59:26 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     corbet@....net, mike.kravetz@...cle.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
        paulmck@...nel.org, mchehab+huawei@...nel.org,
        pawan.kumar.gupta@...ux.intel.com, rdunlap@...radead.org,
        oneukum@...e.com, anshuman.khandual@....com, jroedel@...e.de,
        almasrymina@...gle.com, rientjes@...gle.com
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>
Subject: [RFC PATCH 03/24] mm/hugetlb: Introduce a new config HUGETLB_PAGE_FREE_VMEMMAP

The purpose of introducing HUGETLB_PAGE_FREE_VMEMMAP is to configure
whether to enable the feature of freeing unused vmemmap associated
with HugeTLB pages.

Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 fs/Kconfig | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/fs/Kconfig b/fs/Kconfig
index 976e8b9033c4..61e9c08096ca 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -245,6 +245,21 @@ config HUGETLBFS
 config HUGETLB_PAGE
 	def_bool HUGETLBFS
 
+config HUGETLB_PAGE_FREE_VMEMMAP
+	bool "Free unused vmemmap associated with HugeTLB pages"
+	default n
+	depends on HUGETLB_PAGE
+	depends on SPARSEMEM_VMEMMAP
+	depends on HAVE_BOOTMEM_INFO_NODE
+	help
+	  There are many struct page structure associated with each HugeTLB
+	  page. But we only use a few struct page structure. In this case,
+	  it waste some memory. It is better to free the unused struct page
+	  structures to buddy system which can save some memory. For
+	  architectures that support it, say Y here.
+
+	  If unsure, say N.
+
 config MEMFD_CREATE
 	def_bool TMPFS || HUGETLBFS
 
-- 
2.20.1