From 49920d28781dcced10cd30cb9a938e7d045a1c94 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 12 Dec 2016 16:44:50 -0800 Subject: [PATCH] mm: make transparent hugepage size public Test programs want to know the size of a transparent hugepage. While it is commonly the same as the size of a hugetlbfs page (shown as Hugepagesize in /proc/meminfo), that is not always so: powerpc implements transparent hugepages in a different way from hugetlbfs pages, so it's coincidence when their sizes are the same; and x86 and others can support more than one hugetlbfs page size. Add /sys/kernel/mm/transparent_hugepage/hpage_pmd_size to show the THP size in bytes - it's the same for Anonymous and Shmem hugepages. Call it hpage_pmd_size (after HPAGE_PMD_SIZE) rather than hpage_size, in case some transparent support for pud and pgd pages is added later. Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1612052200290.13021@eggly.anvils Signed-off-by: Hugh Dickins Acked-by: Michal Hocko Acked-by: Vlastimil Babka Cc: Greg Thelen Cc: David Rientjes Cc: "Kirill A. Shutemov" Cc: Andrea Arcangeli Cc: "Aneesh Kumar K.V" Cc: Dave Hansen Cc: Dan Williams Cc: Jan Kara Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/vm/transhuge.txt | 5 +++++ mm/huge_memory.c | 10 ++++++++++ 2 files changed, 15 insertions(+) diff --git a/Documentation/vm/transhuge.txt b/Documentation/vm/transhuge.txt index 2ec6adb5a4ce..c4171e4519c2 100644 --- a/Documentation/vm/transhuge.txt +++ b/Documentation/vm/transhuge.txt @@ -136,6 +136,11 @@ or enable it back by writing 1: echo 0 >/sys/kernel/mm/transparent_hugepage/use_zero_page echo 1 >/sys/kernel/mm/transparent_hugepage/use_zero_page +Some userspace (such as a test program, or an optimized memory allocation +library) may want to know the size (in bytes) of a transparent hugepage: + +cat /sys/kernel/mm/transparent_hugepage/hpage_pmd_size + khugepaged will be automatically started when transparent_hugepage/enabled is set to "always" or "madvise, and it'll be automatically shutdown if it's set to "never". diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 2b44ac11178f..cee42cf05477 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -285,6 +285,15 @@ static ssize_t use_zero_page_store(struct kobject *kobj, } static struct kobj_attribute use_zero_page_attr = __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store); + +static ssize_t hpage_pmd_size_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE); +} +static struct kobj_attribute hpage_pmd_size_attr = + __ATTR_RO(hpage_pmd_size); + #ifdef CONFIG_DEBUG_VM static ssize_t debug_cow_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) @@ -307,6 +316,7 @@ static struct attribute *hugepage_attr[] = { &enabled_attr.attr, &defrag_attr.attr, &use_zero_page_attr.attr, + &hpage_pmd_size_attr.attr, #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &shmem_enabled_attr.attr, #endif -- 2.20.1