From: Muchun Song <songmuchun@bytedance.com>
To: corbet@lwn.net, mike.kravetz@oracle.com, tglx@linutronix.de,
mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com,
dave.hansen@linux.intel.com, luto@kernel.org,
peterz@infradead.org, viro@zeniv.linux.org.uk,
akpm@linux-foundation.org, paulmck@kernel.org,
mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com,
rdunlap@infradead.org, oneukum@suse.com,
anshuman.khandual@arm.com, jroedel@suse.de,
almasrymina@google.com, rientjes@google.com, willy@infradead.org,
osalvador@suse.de, mhocko@suse.com, song.bao.hua@hisilicon.com,
david@redhat.com, naoya.horiguchi@nec.com,
joao.m.martins@oracle.com
Cc: duanxiongchun@bytedance.com, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org,
Muchun Song <songmuchun@bytedance.com>,
Miaohe Lin <linmiaohe@huawei.com>
Subject: [PATCH v15 8/8] mm: hugetlb: optimize the code with the help of the compiler
Date: Mon, 8 Feb 2021 16:50:13 +0800 [thread overview]
Message-ID: <20210208085013.89436-9-songmuchun@bytedance.com> (raw)
In-Reply-To: <20210208085013.89436-1-songmuchun@bytedance.com>
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 <songmuchun@bytedance.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
---
include/linux/hugetlb.h | 3 ++-
mm/hugetlb_vmemmap.c | 13 +++++++++++++
2 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 822ab2f5542a..7bfb06e16298 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -878,7 +878,8 @@ 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 a67301a9d19a..2e7e1d6ee458 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -211,6 +211,12 @@ early_param("hugetlb_free_vmemmap", early_hugetlb_free_vmemmap_param);
*/
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;
}
@@ -280,6 +286,13 @@ 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;
--
2.11.0
prev parent reply other threads:[~2021-02-08 9:12 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-08 8:50 [PATCH v15 0/8] Free some vmemmap pages of HugeTLB page Muchun Song
2021-02-08 8:50 ` [PATCH v15 1/8] mm: memory_hotplug: factor out bootmem core functions to bootmem_info.c Muchun Song
2021-02-08 8:50 ` [PATCH v15 2/8] mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP Muchun Song
2021-02-08 8:50 ` [PATCH v15 3/8] mm: hugetlb: free the vmemmap pages associated with each HugeTLB page Muchun Song
2021-02-08 8:50 ` [PATCH v15 4/8] mm: hugetlb: alloc " Muchun Song
2021-02-11 18:05 ` Mike Kravetz
2021-02-12 14:15 ` David Hildenbrand
2021-02-12 15:32 ` Michal Hocko
2021-02-15 10:05 ` [External] " Muchun Song
2021-02-15 10:33 ` Michal Hocko
2021-02-15 11:51 ` Muchun Song
2021-02-15 12:00 ` Muchun Song
2021-02-15 12:18 ` Michal Hocko
2021-02-15 12:44 ` Muchun Song
2021-02-15 13:19 ` Michal Hocko
2021-02-15 15:36 ` Muchun Song
2021-02-15 16:27 ` Michal Hocko
2021-02-15 17:48 ` Muchun Song
2021-02-15 18:19 ` Muchun Song
2021-02-15 19:39 ` Michal Hocko
2021-02-16 4:34 ` Muchun Song
2021-02-16 8:15 ` Michal Hocko
2021-02-16 8:20 ` David Hildenbrand
2021-02-16 9:03 ` Muchun Song
2021-02-15 19:02 ` Michal Hocko
2021-02-16 8:13 ` David Hildenbrand
2021-02-16 8:21 ` Michal Hocko
2021-02-16 19:44 ` Mike Kravetz
2021-02-17 8:13 ` Michal Hocko
2021-02-18 1:00 ` Mike Kravetz
2021-02-18 3:20 ` Muchun Song
2021-02-18 8:21 ` Michal Hocko
2021-02-15 12:24 ` Michal Hocko
2021-02-08 8:50 ` [PATCH v15 5/8] mm: hugetlb: add a kernel parameter hugetlb_free_vmemmap Muchun Song
2021-02-08 8:50 ` [PATCH v15 6/8] mm: hugetlb: introduce nr_free_vmemmap_pages in the struct hstate Muchun Song
2021-02-08 8:50 ` [PATCH v15 7/8] mm: hugetlb: gather discrete indexes of tail page Muchun Song
2021-02-08 8:50 ` Muchun Song [this message]
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