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Message-ID: <20201216144052.GF29394@linux>
Date: Wed, 16 Dec 2020 15:40:53 +0100
From: Oscar Salvador <osalvador@...e.de>
To: Muchun Song <songmuchun@...edance.com>
Cc: corbet@....net, mike.kravetz@...cle.com, tglx@...utronix.de,
mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
paulmck@...nel.org, mchehab+huawei@...nel.org,
pawan.kumar.gupta@...ux.intel.com, rdunlap@...radead.org,
oneukum@...e.com, anshuman.khandual@....com, jroedel@...e.de,
almasrymina@...gle.com, rientjes@...gle.com, willy@...radead.org,
mhocko@...e.com, song.bao.hua@...ilicon.com, david@...hat.com,
duanxiongchun@...edance.com, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v9 08/11] mm/hugetlb: Add a kernel parameter
hugetlb_free_vmemmap
On Sun, Dec 13, 2020 at 11:45:31PM +0800, Muchun Song wrote:
> Add a kernel parameter hugetlb_free_vmemmap to disable the feature of
> freeing unused vmemmap pages associated with each hugetlb page on boot.
I guess this should read "to enable the feature"?
AFAICS, it is disabled by default.
> Signed-off-by: Muchun Song <songmuchun@...edance.com>
Reviewed-by: Oscar Salvador <osalvador@...e.de>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 9 +++++++++
> Documentation/admin-guide/mm/hugetlbpage.rst | 3 +++
> arch/x86/mm/init_64.c | 8 ++++++--
> include/linux/hugetlb.h | 19 +++++++++++++++++++
> mm/hugetlb_vmemmap.c | 16 ++++++++++++++++
> 5 files changed, 53 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 3ae25630a223..9e6854f21d55 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1551,6 +1551,15 @@
> 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.
> + 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..1bce5f20e6ca 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -34,6 +34,7 @@
> #include <linux/gfp.h>
> #include <linux/kcore.h>
> #include <linux/bootmem_info.h>
> +#include <linux/hugetlb.h>
>
> #include <asm/processor.h>
> #include <asm/bios_ebda.h>
> @@ -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() ||
> + 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 ebca2ef02212..7f47f0eeca3b 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -770,6 +770,20 @@ static inline void huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
> }
> #endif
>
> +#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 {};
>
> @@ -923,6 +937,11 @@ 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 02201c2e3dfa..64ad929cac61 100644
> --- a/mm/hugetlb_vmemmap.c
> +++ b/mm/hugetlb_vmemmap.c
> @@ -180,6 +180,22 @@
> #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)
> +{
> + 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);
> +
> static inline unsigned long free_vmemmap_pages_size_per_hpage(struct hstate *h)
> {
> return (unsigned long)free_vmemmap_pages_per_hpage(h) << PAGE_SHIFT;
> --
> 2.11.0
>
--
Oscar Salvador
SUSE L3
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