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Date: Wed, 28 Oct 2020 16:42:29 -0700
From: Mike Kravetz <mike.kravetz@...cle.com>
To: Muchun Song <songmuchun@...edance.com>, corbet@....net,
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
Cc: 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 v2 07/19] mm/hugetlb: Free the vmemmap pages associated
with each hugetlb page
On 10/26/20 7:51 AM, Muchun Song wrote:
> When we allocate a hugetlb page from the buddy, we should free the
> unused vmemmap pages associated with it. We can do that in the
> prep_new_huge_page().
>
> Signed-off-by: Muchun Song <songmuchun@...edance.com>
> ---
> arch/x86/include/asm/hugetlb.h | 7 +
> arch/x86/include/asm/pgtable_64_types.h | 8 +
> include/linux/hugetlb.h | 7 +
> mm/hugetlb.c | 190 ++++++++++++++++++++++++
> 4 files changed, 212 insertions(+)
>
> diff --git a/arch/x86/include/asm/hugetlb.h b/arch/x86/include/asm/hugetlb.h
> index f5e882f999cd..7c3eb60c2198 100644
> --- a/arch/x86/include/asm/hugetlb.h
> +++ b/arch/x86/include/asm/hugetlb.h
> @@ -4,10 +4,17 @@
>
> #include <asm/page.h>
> #include <asm-generic/hugetlb.h>
> +#include <asm/pgtable.h>
>
> #ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP
> #define VMEMMAP_HPAGE_SHIFT PMD_SHIFT
> #define arch_vmemmap_support_huge_mapping() boot_cpu_has(X86_FEATURE_PSE)
> +
> +#define vmemmap_pmd_huge vmemmap_pmd_huge
> +static inline bool vmemmap_pmd_huge(pmd_t *pmd)
> +{
> + return pmd_large(*pmd);
> +}
> #endif
>
> #define hugepages_supported() boot_cpu_has(X86_FEATURE_PSE)
> diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h
> index 52e5f5f2240d..bedbd2e7d06c 100644
> --- a/arch/x86/include/asm/pgtable_64_types.h
> +++ b/arch/x86/include/asm/pgtable_64_types.h
> @@ -139,6 +139,14 @@ extern unsigned int ptrs_per_p4d;
> # define VMEMMAP_START __VMEMMAP_BASE_L4
> #endif /* CONFIG_DYNAMIC_MEMORY_LAYOUT */
>
> +/*
> + * VMEMMAP_SIZE - allows the whole linear region to be covered by
> + * a struct page array.
> + */
> +#define VMEMMAP_SIZE (1UL << (__VIRTUAL_MASK_SHIFT - PAGE_SHIFT - \
> + 1 + ilog2(sizeof(struct page))))
> +#define VMEMMAP_END (VMEMMAP_START + VMEMMAP_SIZE)
> +
> #define VMALLOC_END (VMALLOC_START + (VMALLOC_SIZE_TB << 40) - 1)
>
> #define MODULES_VADDR (__START_KERNEL_map + KERNEL_IMAGE_SIZE)
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index ace304a6196c..919f47d77117 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -601,6 +601,13 @@ static inline bool arch_vmemmap_support_huge_mapping(void)
> }
> #endif
>
> +#ifndef vmemmap_pmd_huge
Let's add
#define vmemmap_pmd_huge vmemmap_pmd_huge
just in case code gets moved around in header file.
> +static inline bool vmemmap_pmd_huge(pmd_t *pmd)
> +{
> + return pmd_huge(*pmd);
> +}
> +#endif
> +
> #ifndef VMEMMAP_HPAGE_SHIFT
> #define VMEMMAP_HPAGE_SHIFT PMD_SHIFT
> #endif
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index d6ae9b6876be..aa012d603e06 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1293,10 +1293,20 @@ static inline void destroy_compound_gigantic_page(struct page *page,
> #endif
>
> #ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP
> +#include <linux/bootmem_info.h>
> +
> #define RESERVE_VMEMMAP_NR 2U
> +#define RESERVE_VMEMMAP_SIZE (RESERVE_VMEMMAP_NR << PAGE_SHIFT)
Since RESERVE_VMEMMAP_SIZE is not used here, perhaps it should be added
in the patch where it is first used.
>
> #define page_huge_pte(page) ((page)->pmd_huge_pte)
>
> +#define vmemmap_hpage_addr_end(addr, end) \
> +({ \
> + unsigned long __boundary; \
> + __boundary = ((addr) + VMEMMAP_HPAGE_SIZE) & VMEMMAP_HPAGE_MASK;\
> + (__boundary - 1 < (end) - 1) ? __boundary : (end); \
> +})
> +
> static inline unsigned int nr_free_vmemmap(struct hstate *h)
> {
> return h->nr_free_vmemmap_pages;
> @@ -1416,6 +1426,181 @@ static void __init hugetlb_vmemmap_init(struct hstate *h)
> pr_info("HugeTLB: can free %d vmemmap pages for %s\n",
> h->nr_free_vmemmap_pages, h->name);
> }
> +
> +static inline spinlock_t *vmemmap_pmd_lockptr(pmd_t *pmd)
> +{
> + static DEFINE_SPINLOCK(pgtable_lock);
> +
> + return &pgtable_lock;
> +}
This is just a global lock. Correct? And hugetlb specific?
It should be OK as the page table entries for huegtlb pages will not
overlap with other entries.
> +
> +/*
> + * Walk a vmemmap address to the pmd it maps.
> + */
> +static pmd_t *vmemmap_to_pmd(const void *page)
> +{
> + unsigned long addr = (unsigned long)page;
> + pgd_t *pgd;
> + p4d_t *p4d;
> + pud_t *pud;
> + pmd_t *pmd;
> +
> + if (addr < VMEMMAP_START || addr >= VMEMMAP_END)
> + return NULL;
> +
> + pgd = pgd_offset_k(addr);
> + if (pgd_none(*pgd))
> + return NULL;
> + p4d = p4d_offset(pgd, addr);
> + if (p4d_none(*p4d))
> + return NULL;
> + pud = pud_offset(p4d, addr);
> +
> + WARN_ON_ONCE(pud_bad(*pud));
> + if (pud_none(*pud) || pud_bad(*pud))
> + return NULL;
> + pmd = pmd_offset(pud, addr);
> +
> + return pmd;
> +}
That routine is not really hugetlb specific. Perhaps we could move it
to sparse-vmemmap.c? Or elsewhere?
--
Mike Kravetz
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