From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.6 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 936E2C433E0 for ; Fri, 5 Feb 2021 07:26:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5202164E0B for ; Fri, 5 Feb 2021 07:26:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231421AbhBEH0Y (ORCPT ); Fri, 5 Feb 2021 02:26:24 -0500 Received: from szxga05-in.huawei.com ([45.249.212.191]:12466 "EHLO szxga05-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230486AbhBEH0Q (ORCPT ); Fri, 5 Feb 2021 02:26:16 -0500 Received: from DGGEMS410-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4DX6Nr38k6zjKjh; Fri, 5 Feb 2021 15:24:12 +0800 (CST) Received: from [10.174.179.241] (10.174.179.241) by DGGEMS410-HUB.china.huawei.com (10.3.19.210) with Microsoft SMTP Server id 14.3.498.0; Fri, 5 Feb 2021 15:25:25 +0800 Subject: Re: [PATCH v14 5/8] mm: hugetlb: add a kernel parameter hugetlb_free_vmemmap To: Muchun Song CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , References: <20210204035043.36609-1-songmuchun@bytedance.com> <20210204035043.36609-6-songmuchun@bytedance.com> From: Miaohe Lin Message-ID: <75172dd1-8948-62b7-4ad8-f158785fd6b9@huawei.com> Date: Fri, 5 Feb 2021 15:25:24 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20210204035043.36609-6-songmuchun@bytedance.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.179.241] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi: On 2021/2/4 11:50, Muchun Song wrote: > Add a kernel parameter hugetlb_free_vmemmap to enable the feature of > freeing unused vmemmap pages associated with each hugetlb page on boot. > > We disables PMD mapping of vmemmap pages for x86-64 arch when this > feature is enabled. Because vmemmap_remap_free() depends on vmemmap > being base page mapped. > > Signed-off-by: Muchun Song > Reviewed-by: Oscar Salvador > Reviewed-by: Barry Song Looks good to me. Thanks. Reviewed-by: Miaohe Lin > --- > Documentation/admin-guide/kernel-parameters.txt | 14 ++++++++++++++ > Documentation/admin-guide/mm/hugetlbpage.rst | 3 +++ > arch/x86/mm/init_64.c | 8 ++++++-- > include/linux/hugetlb.h | 19 +++++++++++++++++++ > mm/hugetlb_vmemmap.c | 22 ++++++++++++++++++++++ > 5 files changed, 64 insertions(+), 2 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 5adf1e57e932..7db2591f3ad3 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -1577,6 +1577,20 @@ > Documentation/admin-guide/mm/hugetlbpage.rst. > Format: size[KMG] > > + hugetlb_free_vmemmap= > + [KNL] When CONFIG_HUGETLB_PAGE_FREE_VMEMMAP is set, > + this controls freeing unused vmemmap pages associated > + with each HugeTLB page. When this option is enabled, > + we disable PMD/huge page mapping of vmemmap pages which > + increase page table pages. So if a user/sysadmin only > + uses a small number of HugeTLB pages (as a percentage > + of system memory), they could end up using more memory > + with hugetlb_free_vmemmap on as opposed to off. > + Format: { on | off (default) } > + > + on: enable the feature > + off: disable the feature > + > hung_task_panic= > [KNL] Should the hung task detector generate panics. > Format: 0 | 1 > diff --git a/Documentation/admin-guide/mm/hugetlbpage.rst b/Documentation/admin-guide/mm/hugetlbpage.rst > index f7b1c7462991..3a23c2377acc 100644 > --- a/Documentation/admin-guide/mm/hugetlbpage.rst > +++ b/Documentation/admin-guide/mm/hugetlbpage.rst > @@ -145,6 +145,9 @@ default_hugepagesz > > will all result in 256 2M huge pages being allocated. Valid default > huge page size is architecture dependent. > +hugetlb_free_vmemmap > + When CONFIG_HUGETLB_PAGE_FREE_VMEMMAP is set, this enables freeing > + unused vmemmap pages associated with each HugeTLB page. > > When multiple huge page sizes are supported, ``/proc/sys/vm/nr_hugepages`` > indicates the current number of pre-allocated huge pages of the default size. > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c > index 0435bee2e172..39f88c5faadc 100644 > --- a/arch/x86/mm/init_64.c > +++ b/arch/x86/mm/init_64.c > @@ -34,6 +34,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -1557,7 +1558,8 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node, > { > int err; > > - if (end - start < PAGES_PER_SECTION * sizeof(struct page)) > + if ((is_hugetlb_free_vmemmap_enabled() && !altmap) || > + end - start < PAGES_PER_SECTION * sizeof(struct page)) > err = vmemmap_populate_basepages(start, end, node, NULL); > else if (boot_cpu_has(X86_FEATURE_PSE)) > err = vmemmap_populate_hugepages(start, end, node, altmap); > @@ -1585,6 +1587,8 @@ void register_page_bootmem_memmap(unsigned long section_nr, > pmd_t *pmd; > unsigned int nr_pmd_pages; > struct page *page; > + bool base_mapping = !boot_cpu_has(X86_FEATURE_PSE) || > + is_hugetlb_free_vmemmap_enabled(); > > for (; addr < end; addr = next) { > pte_t *pte = NULL; > @@ -1610,7 +1614,7 @@ void register_page_bootmem_memmap(unsigned long section_nr, > } > get_page_bootmem(section_nr, pud_page(*pud), MIX_SECTION_INFO); > > - if (!boot_cpu_has(X86_FEATURE_PSE)) { > + if (base_mapping) { > next = (addr + PAGE_SIZE) & PAGE_MASK; > pmd = pmd_offset(pud, addr); > if (pmd_none(*pmd)) > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index 37fd248ce271..ad249e56ac49 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -854,6 +854,20 @@ static inline void huge_ptep_modify_prot_commit(struct vm_area_struct *vma, > > void set_page_huge_active(struct page *page); > > +#ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP > +extern bool hugetlb_free_vmemmap_enabled; > + > +static inline bool is_hugetlb_free_vmemmap_enabled(void) > +{ > + return hugetlb_free_vmemmap_enabled; > +} > +#else > +static inline bool is_hugetlb_free_vmemmap_enabled(void) > +{ > + return false; > +} > +#endif > + > #else /* CONFIG_HUGETLB_PAGE */ > struct hstate {}; > > @@ -1007,6 +1021,11 @@ static inline void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr > pte_t *ptep, pte_t pte, unsigned long sz) > { > } > + > +static inline bool is_hugetlb_free_vmemmap_enabled(void) > +{ > + return false; > +} > #endif /* CONFIG_HUGETLB_PAGE */ > > static inline spinlock_t *huge_pte_lock(struct hstate *h, > diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c > index 0bd6b8d7282d..224a3cb69bf9 100644 > --- a/mm/hugetlb_vmemmap.c > +++ b/mm/hugetlb_vmemmap.c > @@ -183,6 +183,28 @@ > #define RESERVE_VMEMMAP_NR 2U > #define RESERVE_VMEMMAP_SIZE (RESERVE_VMEMMAP_NR << PAGE_SHIFT) > > +bool hugetlb_free_vmemmap_enabled; > + > +static int __init early_hugetlb_free_vmemmap_param(char *buf) > +{ > + /* We cannot optimize if a "struct page" crosses page boundaries. */ > + if ((!is_power_of_2(sizeof(struct page)))) { > + pr_warn("cannot free vmemmap pages because \"struct page\" crosses page boundaries\n"); > + return 0; > + } > + > + if (!buf) > + return -EINVAL; > + > + if (!strcmp(buf, "on")) > + hugetlb_free_vmemmap_enabled = true; > + else if (strcmp(buf, "off")) > + return -EINVAL; > + > + return 0; > +} > +early_param("hugetlb_free_vmemmap", early_hugetlb_free_vmemmap_param); > + > /* > * How many vmemmap pages associated with a HugeTLB page that can be freed > * to the buddy allocator. >