[PATCH v18 9/9] mm: hugetlb: optimize the code with the help of the compiler
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STALE2055d
SUPERSEDED: 4 (2M)
From: Muchun Song <hidden>
Date: 2021-03-08 10:33:11
Also in:
linux-fsdevel, linux-mm, lkml
Subsystem:
hugetlb subsystem, memory management, the rest · Maintainers:
Muchun Song, Oscar Salvador, Andrew Morton, Linus Torvalds
Status: Superseded by v23 (posted 2021-05-10). [go to v23]
Revision v18 (19 revisions archived); 4 review trailers (1 from subsystem maintainers).
Revisions (19)
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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. Signed-off-by: Muchun Song <redacted> Reviewed-by: Miaohe Lin <linmiaohe@huawei.com> Reviewed-by: Oscar Salvador <osalvador@suse.de> Tested-by: Chen Huang <redacted> Tested-by: Bodeddula Balasubramaniam <redacted> --- include/linux/hugetlb.h | 3 ++- mm/hugetlb_vmemmap.c | 7 +++++++ mm/hugetlb_vmemmap.h | 6 ++++++ 3 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index c70421e26189..333dd0479fc2 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h@@ -880,7 +880,8 @@ 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)
diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index 33e42678abe3..1ba1ef45c48c 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c@@ -265,6 +265,13 @@ void __init hugetlb_vmemmap_init(struct hstate *h) 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;
diff --git a/mm/hugetlb_vmemmap.h b/mm/hugetlb_vmemmap.h
index cb2bef8f9e73..29aaaf7b741e 100644
--- a/mm/hugetlb_vmemmap.h
+++ b/mm/hugetlb_vmemmap.h@@ -21,6 +21,12 @@ void hugetlb_vmemmap_init(struct hstate *h); */ 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
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2.11.0