From: Michal Hocko <mhocko@suse.com>
To: Muchun Song <songmuchun@bytedance.com>
Cc: 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, song.bao.hua@hisilicon.com, david@redhat.com,
naoya.horiguchi@nec.com, joao.m.martins@oracle.com,
duanxiongchun@bytedance.com, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org, Miaohe Lin <linmiaohe@huawei.com>,
Chen Huang <chenhuang5@huawei.com>,
Bodeddula Balasubramaniam <bodeddub@amazon.com>
Subject: Re: [PATCH v18 9/9] mm: hugetlb: optimize the code with the help of the compiler
Date: Wed, 10 Mar 2021 16:41:23 +0100 [thread overview]
Message-ID: <YEjoozshsvKeMAAu@dhcp22.suse.cz> (raw)
In-Reply-To: <20210308102807.59745-10-songmuchun@bytedance.com>
On Mon 08-03-21 18:28:07, Muchun Song wrote:
> 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.
I am confused. Don't you check for this in early_hugetlb_free_vmemmap_param already?
Why do we need any runtime checks?
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
> Reviewed-by: Oscar Salvador <osalvador@suse.de>
> Tested-by: Chen Huang <chenhuang5@huawei.com>
> Tested-by: Bodeddula Balasubramaniam <bodeddub@amazon.com>
> ---
> 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
> --
> 2.11.0
>
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-03-10 15:41 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-08 10:27 [PATCH v18 0/9] Free some vmemmap pages of HugeTLB page Muchun Song
2021-03-08 10:27 ` [PATCH v18 1/9] mm: memory_hotplug: factor out bootmem core functions to bootmem_info.c Muchun Song
2021-03-10 14:14 ` Michal Hocko
2021-03-11 2:58 ` [External] " Muchun Song
2021-03-11 8:45 ` Muchun Song
2021-03-11 8:53 ` Michal Hocko
2021-03-11 9:05 ` Muchun Song
2021-03-08 10:28 ` [PATCH v18 2/9] mm: hugetlb: introduce a new config HUGETLB_PAGE_FREE_VMEMMAP Muchun Song
2021-03-08 10:28 ` [PATCH v18 3/9] mm: hugetlb: free the vmemmap pages associated with each HugeTLB page Muchun Song
2021-03-10 14:32 ` Michal Hocko
2021-03-11 3:35 ` [External] " Muchun Song
2021-03-08 10:28 ` [PATCH v18 4/9] mm: hugetlb: alloc " Muchun Song
2021-03-10 14:21 ` Oscar Salvador
2021-03-11 4:13 ` [External] " Muchun Song
2021-03-10 15:19 ` Michal Hocko
2021-03-10 18:56 ` Mike Kravetz
2021-03-10 21:11 ` Michal Hocko
2021-03-10 21:49 ` Paul E. McKenney
2021-03-10 22:10 ` Mike Kravetz
2021-03-10 23:28 ` Paul E. McKenney
2021-03-11 8:40 ` Michal Hocko
2021-03-11 12:17 ` Michal Hocko
2021-03-11 17:59 ` Mike Kravetz
2021-03-11 22:53 ` Mike Kravetz
2021-03-12 8:15 ` Michal Hocko
2021-03-12 17:50 ` Mike Kravetz
2021-03-11 4:26 ` [External] " Muchun Song
2021-03-11 8:46 ` Michal Hocko
2021-03-11 8:49 ` Muchun Song
2021-03-08 10:28 ` [PATCH v18 5/9] mm: hugetlb: set the PageHWPoison to the raw error page Muchun Song
2021-03-10 15:27 ` Michal Hocko
2021-03-11 6:34 ` [External] " Muchun Song
2021-03-11 8:50 ` Michal Hocko
2021-03-11 9:13 ` Muchun Song
2021-03-08 10:28 ` [PATCH v18 6/9] mm: hugetlb: add a kernel parameter hugetlb_free_vmemmap Muchun Song
2021-03-10 15:37 ` Michal Hocko
2021-03-10 17:15 ` Randy Dunlap
2021-03-11 6:36 ` [External] " Muchun Song
2021-03-11 6:36 ` Muchun Song
2021-03-08 10:28 ` [PATCH v18 7/9] mm: hugetlb: introduce nr_free_vmemmap_pages in the struct hstate Muchun Song
2021-03-08 10:28 ` [PATCH v18 8/9] mm: hugetlb: gather discrete indexes of tail page Muchun Song
2021-03-10 15:39 ` Michal Hocko
2021-03-08 10:28 ` [PATCH v18 9/9] mm: hugetlb: optimize the code with the help of the compiler Muchun Song
2021-03-10 15:41 ` Michal Hocko [this message]
2021-03-11 7:33 ` [External] " Muchun Song
2021-03-11 8:55 ` Michal Hocko
2021-03-11 9:08 ` Muchun Song
2021-03-11 9:39 ` Michal Hocko
2021-03-11 10:00 ` Muchun Song
2021-03-11 12:16 ` Michal Hocko
2021-03-11 13:00 ` Muchun Song
2021-03-11 13:45 ` Oscar Salvador
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