The patch titled
Subject: mm: hugetlb: optimize the code with the help of the compiler
has been added to the -mm tree. Its filename is
mm-hugetlb-optimize-the-code-with-the-help-of-the-compiler.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-hugetlb-optimize-the-code-with-the-help-of-the-compiler.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlb-optimize-the-code-with-the-help-of-the-compiler.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Subject: mm: hugetlb: optimize the code with the help of the compiler
When the "struct page size" crosses page boundaries we cannot make use of
this feature. Let free_vmemmap_pages_per_hpage() return zero if that is
the case, most of the functions can be optimized away.
Link: https://lkml.kernel.org/r/20210308102807.59745-10-songmuchun@xxxxxxxxxxxxx
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
Tested-by: Chen Huang <chenhuang5@xxxxxxxxxx>
Tested-by: Bodeddula Balasubramaniam <bodeddub@xxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Balbir Singh <bsingharora@xxxxxxxxx>
Cc: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Joao Martins <joao.m.martins@xxxxxxxxxx>
Cc: Joerg Roedel <jroedel@xxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mina Almasry <almasrymina@xxxxxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Cc: Oliver Neukum <oneukum@xxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Xiongchun Duan <duanxiongchun@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/hugetlb.h | 3 ++-
mm/hugetlb_vmemmap.c | 7 +++++++
mm/hugetlb_vmemmap.h | 6 ++++++
3 files changed, 15 insertions(+), 1 deletion(-)
--- a/include/linux/hugetlb.h~mm-hugetlb-optimize-the-code-with-the-help-of-the-compiler
+++ a/include/linux/hugetlb.h
@@ -894,7 +894,8 @@ extern bool hugetlb_free_vmemmap_enabled
static inline bool is_hugetlb_free_vmemmap_enabled(void)
{
- return hugetlb_free_vmemmap_enabled;
+ return hugetlb_free_vmemmap_enabled &&
+ is_power_of_2(sizeof(struct page));
}
#else
static inline bool is_hugetlb_free_vmemmap_enabled(void)
--- a/mm/hugetlb_vmemmap.c~mm-hugetlb-optimize-the-code-with-the-help-of-the-compiler
+++ a/mm/hugetlb_vmemmap.c
@@ -265,6 +265,13 @@ void __init hugetlb_vmemmap_init(struct
BUILD_BUG_ON(__NR_USED_SUBPAGE >=
RESERVE_VMEMMAP_SIZE / sizeof(struct page));
+ /*
+ * The compiler can help us to optimize this function to null
+ * when the size of the struct page is not power of 2.
+ */
+ if (!is_power_of_2(sizeof(struct page)))
+ return;
+
if (!hugetlb_free_vmemmap_enabled)
return;
--- a/mm/hugetlb_vmemmap.h~mm-hugetlb-optimize-the-code-with-the-help-of-the-compiler
+++ a/mm/hugetlb_vmemmap.h
@@ -21,6 +21,12 @@ void hugetlb_vmemmap_init(struct hstate
*/
static inline unsigned int free_vmemmap_pages_per_hpage(struct hstate *h)
{
+ /*
+ * This check aims to let the compiler help us optimize the code as
+ * much as possible.
+ */
+ if (!is_power_of_2(sizeof(struct page)))
+ return 0;
return h->nr_free_vmemmap_pages;
}
#else
_
Patches currently in -mm which might be from songmuchun@xxxxxxxxxxxxx are
mm-memcontrol-fix-kernel-stack-account.patch
mm-memory_hotplug-factor-out-bootmem-core-functions-to-bootmem_infoc.patch
mm-hugetlb-introduce-a-new-config-hugetlb_page_free_vmemmap.patch
mm-hugetlb-free-the-vmemmap-pages-associated-with-each-hugetlb-page.patch
mm-hugetlb-alloc-the-vmemmap-pages-associated-with-each-hugetlb-page.patch
mm-hugetlb-set-the-pagehwpoison-to-the-raw-error-page.patch
mm-hugetlb-add-a-kernel-parameter-hugetlb_free_vmemmap.patch
mm-hugetlb-introduce-nr_free_vmemmap_pages-in-the-struct-hstate.patch
mm-hugetlb-gather-discrete-indexes-of-tail-page.patch
mm-hugetlb-optimize-the-code-with-the-help-of-the-compiler.patch
