From: Miaohe Lin <linmiaohe@huawei.com>
To: Muchun Song <songmuchun@bytedance.com>
Cc: <duanxiongchun@bytedance.com>, <linux-doc@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
<linux-fsdevel@vger.kernel.org>, <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>
Subject: Re: [PATCH v14 8/8] mm: hugetlb: optimize the code with the help of the compiler
Date: Thu, 4 Feb 2021 14:33:42 +0800 [thread overview]
Message-ID: <657ef0d7-8c68-a0f2-de16-d524f0eb4cc7@huawei.com> (raw)
In-Reply-To: <20210204035043.36609-9-songmuchun@bytedance.com>
On 2021/2/4 11:50, Muchun Song wrote:
> We cannot optimize if a "struct page" crosses page boundaries. If
> it is true, we can optimize the code with the help of a compiler.
> When free_vmemmap_pages_per_hpage() returns zero, most functions are
> optimized by the compiler.
>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
I like it. Thanks.
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
> 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 8efad9978821..068d0e0cebc8 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;
>
>
next prev parent reply other threads:[~2021-02-04 6:34 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-04 3:50 [PATCH v14 0/8] Free some vmemmap pages of HugeTLB page Muchun Song
2021-02-04 3:50 ` [PATCH v14 1/8] mm: memory_hotplug: factor out bootmem core functions to bootmem_info.c Muchun Song
2021-02-04 3:50 ` [PATCH v14 2/8] mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP Muchun Song
2021-02-04 11:44 ` Miaohe Lin
2021-02-04 3:50 ` [PATCH v14 3/8] mm: hugetlb: free the vmemmap pages associated with each HugeTLB page Muchun Song
2021-02-05 8:54 ` Oscar Salvador
2021-02-05 16:01 ` [External] " Muchun Song
2021-02-04 3:50 ` [PATCH v14 4/8] mm: hugetlb: alloc " Muchun Song
2021-02-05 9:29 ` Muchun Song
2021-02-05 11:54 ` Oscar Salvador
2021-02-06 8:01 ` [External] " Muchun Song
2021-02-04 3:50 ` [PATCH v14 5/8] mm: hugetlb: add a kernel parameter hugetlb_free_vmemmap Muchun Song
2021-02-05 7:25 ` Miaohe Lin
2021-02-04 3:50 ` [PATCH v14 6/8] mm: hugetlb: introduce nr_free_vmemmap_pages in the struct hstate Muchun Song
2021-02-05 7:29 ` Miaohe Lin
2021-02-05 8:22 ` Oscar Salvador
2021-02-05 8:39 ` Miaohe Lin
2021-02-05 8:56 ` Oscar Salvador
2021-02-05 9:12 ` Miaohe Lin
2021-02-04 3:50 ` [PATCH v14 7/8] mm: hugetlb: gather discrete indexes of tail page Muchun Song
2021-02-05 7:30 ` Miaohe Lin
2021-02-04 3:50 ` [PATCH v14 8/8] mm: hugetlb: optimize the code with the help of the compiler Muchun Song
2021-02-04 6:33 ` Miaohe Lin [this message]
2021-02-05 9:09 ` Oscar Salvador
2021-02-05 9:16 ` [External] " Muchun Song
2021-02-05 8:59 ` [PATCH v14 0/8] Free some vmemmap pages of HugeTLB page Oscar Salvador
2021-02-05 9:30 ` [External] " Muchun Song
2021-02-05 16:00 ` Joao Martins
2021-02-05 16:13 ` [External] " Muchun Song
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