Linux-Fsdevel Archive on lore.kernel.org
 help / color / Atom feed
From: Mike Kravetz <mike.kravetz@oracle.com>
To: Muchun Song <songmuchun@bytedance.com>,
	corbet@lwn.net, 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
Cc: duanxiongchun@bytedance.com, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v2 05/19] mm/hugetlb: Introduce pgtable allocation/freeing helpers
Date: Tue, 27 Oct 2020 17:32:56 -0700
Message-ID: <81a7a7f0-fe0e-42e4-8de0-9092b033addc@oracle.com> (raw)
In-Reply-To: <20201026145114.59424-6-songmuchun@bytedance.com>

On 10/26/20 7:51 AM, Muchun Song wrote:
> On some architectures, the vmemmap areas use huge page mapping.
> If we want to free the unused vmemmap pages, we have to split
> the huge pmd firstly. So we should pre-allocate pgtable to split
> huge pmd.
> 
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> ---
>  arch/x86/include/asm/hugetlb.h |   5 ++
>  include/linux/hugetlb.h        |  17 +++++
>  mm/hugetlb.c                   | 117 +++++++++++++++++++++++++++++++++
>  3 files changed, 139 insertions(+)
> 
> diff --git a/arch/x86/include/asm/hugetlb.h b/arch/x86/include/asm/hugetlb.h
> index 1721b1aadeb1..f5e882f999cd 100644
> --- a/arch/x86/include/asm/hugetlb.h
> +++ b/arch/x86/include/asm/hugetlb.h
> @@ -5,6 +5,11 @@
>  #include <asm/page.h>
>  #include <asm-generic/hugetlb.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)
> +#endif
> +
>  #define hugepages_supported() boot_cpu_has(X86_FEATURE_PSE)
>  
>  #endif /* _ASM_X86_HUGETLB_H */
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index eed3dd3bd626..ace304a6196c 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -593,6 +593,23 @@ static inline unsigned int blocks_per_huge_page(struct hstate *h)
>  
>  #include <asm/hugetlb.h>
>  
> +#ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP
> +#ifndef arch_vmemmap_support_huge_mapping
> +static inline bool arch_vmemmap_support_huge_mapping(void)
> +{
> +	return false;
> +}
> +#endif
> +
> +#ifndef VMEMMAP_HPAGE_SHIFT
> +#define VMEMMAP_HPAGE_SHIFT		PMD_SHIFT
> +#endif
> +#define VMEMMAP_HPAGE_ORDER		(VMEMMAP_HPAGE_SHIFT - PAGE_SHIFT)
> +#define VMEMMAP_HPAGE_NR		(1 << VMEMMAP_HPAGE_ORDER)
> +#define VMEMMAP_HPAGE_SIZE		((1UL) << VMEMMAP_HPAGE_SHIFT)
> +#define VMEMMAP_HPAGE_MASK		(~(VMEMMAP_HPAGE_SIZE - 1))
> +#endif /* CONFIG_HUGETLB_PAGE_FREE_VMEMMAP */
> +
>  #ifndef is_hugepage_only_range
>  static inline int is_hugepage_only_range(struct mm_struct *mm,
>  					unsigned long addr, unsigned long len)
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index f1b2b733b49b..d6ae9b6876be 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1295,11 +1295,108 @@ static inline void destroy_compound_gigantic_page(struct page *page,
>  #ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP
>  #define RESERVE_VMEMMAP_NR	2U
>  
> +#define page_huge_pte(page)	((page)->pmd_huge_pte)
> +

I am not good at function names.  The following suggestions may be too
verbose.  However, they helped me understand purpose of routines.

>  static inline unsigned int nr_free_vmemmap(struct hstate *h)

	perhaps?	 	free_vmemmap_pages_per_hpage()

>  {
>  	return h->nr_free_vmemmap_pages;
>  }
>  
> +static inline unsigned int nr_vmemmap(struct hstate *h)

	perhaps?		vmemmap_pages_per_hpage()

> +{
> +	return nr_free_vmemmap(h) + RESERVE_VMEMMAP_NR;
> +}
> +
> +static inline unsigned long nr_vmemmap_size(struct hstate *h)

	perhaps?		vmemmap_pages_size_per_hpage()

> +{
> +	return (unsigned long)nr_vmemmap(h) << PAGE_SHIFT;
> +}
> +
> +static inline unsigned int nr_pgtable(struct hstate *h)

	perhaps?	pgtable_pages_to_prealloc_per_hpage()

> +{
> +	unsigned long vmemmap_size = nr_vmemmap_size(h);
> +
> +	if (!arch_vmemmap_support_huge_mapping())
> +		return 0;
> +
> +	/*
> +	 * No need pre-allocate page tabels when there is no vmemmap pages
> +	 * to free.
> +	 */
> +	if (!nr_free_vmemmap(h))
> +		return 0;
> +
> +	return ALIGN(vmemmap_size, VMEMMAP_HPAGE_SIZE) >> VMEMMAP_HPAGE_SHIFT;
> +}
> +
> +static inline void vmemmap_pgtable_init(struct page *page)
> +{
> +	page_huge_pte(page) = NULL;
> +}
> +

I see the following routines follow the pattern for vmemmap manipulation
in dax.

> +static void vmemmap_pgtable_deposit(struct page *page, pte_t *pte_p)
> +{
> +	pgtable_t pgtable = virt_to_page(pte_p);
> +
> +	/* FIFO */
> +	if (!page_huge_pte(page))
> +		INIT_LIST_HEAD(&pgtable->lru);
> +	else
> +		list_add(&pgtable->lru, &page_huge_pte(page)->lru);
> +	page_huge_pte(page) = pgtable;
> +}
> +
> +static pte_t *vmemmap_pgtable_withdraw(struct page *page)
> +{
> +	pgtable_t pgtable;
> +
> +	/* FIFO */
> +	pgtable = page_huge_pte(page);
> +	if (unlikely(!pgtable))
> +		return NULL;
> +	page_huge_pte(page) = list_first_entry_or_null(&pgtable->lru,
> +						       struct page, lru);
> +	if (page_huge_pte(page))
> +		list_del(&pgtable->lru);
> +	return page_to_virt(pgtable);
> +}
> +
> +static int vmemmap_pgtable_prealloc(struct hstate *h, struct page *page)
> +{
> +	int i;
> +	pte_t *pte_p;
> +	unsigned int nr = nr_pgtable(h);
> +
> +	if (!nr)
> +		return 0;
> +
> +	vmemmap_pgtable_init(page);
> +
> +	for (i = 0; i < nr; i++) {
> +		pte_p = pte_alloc_one_kernel(&init_mm);
> +		if (!pte_p)
> +			goto out;
> +		vmemmap_pgtable_deposit(page, pte_p);
> +	}
> +
> +	return 0;
> +out:
> +	while (i-- && (pte_p = vmemmap_pgtable_withdraw(page)))
> +		pte_free_kernel(&init_mm, pte_p);
> +	return -ENOMEM;
> +}
> +
> +static inline void vmemmap_pgtable_free(struct hstate *h, struct page *page)
> +{
> +	pte_t *pte_p;
> +
> +	if (!nr_pgtable(h))
> +		return;
> +
> +	while ((pte_p = vmemmap_pgtable_withdraw(page)))
> +		pte_free_kernel(&init_mm, pte_p);
> +}
> +
>  static void __init hugetlb_vmemmap_init(struct hstate *h)
>  {
>  	unsigned int order = huge_page_order(h);
> @@ -1323,6 +1420,15 @@ static void __init hugetlb_vmemmap_init(struct hstate *h)
>  static inline void hugetlb_vmemmap_init(struct hstate *h)
>  {
>  }
> +
> +static inline int vmemmap_pgtable_prealloc(struct hstate *h, struct page *page)
> +{
> +	return 0;
> +}
> +
> +static inline void vmemmap_pgtable_free(struct hstate *h, struct page *page)
> +{
> +}
>  #endif
>  
>  static void update_and_free_page(struct hstate *h, struct page *page)
> @@ -1531,6 +1637,9 @@ void free_huge_page(struct page *page)
>  
>  static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
>  {
> +	/* Must be called before the initialization of @page->lru */
> +	vmemmap_pgtable_free(h, page);
> +
>  	INIT_LIST_HEAD(&page->lru);
>  	set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
>  	set_hugetlb_cgroup(page, NULL);
> @@ -1783,6 +1892,14 @@ static struct page *alloc_fresh_huge_page(struct hstate *h,
>  	if (!page)
>  		return NULL;
>  
> +	if (vmemmap_pgtable_prealloc(h, page)) {
> +		if (hstate_is_gigantic(h))
> +			free_gigantic_page(page, huge_page_order(h));
> +		else
> +			put_page(page);
> +		return NULL;
> +	}
> +

It seems a bit strange that we will fail a huge page allocation if
vmemmap_pgtable_prealloc fails.  Not sure, but it almost seems like we shold
allow the allocation and log a warning?  It is somewhat unfortunate that
we need to allocate a page to free pages.

>  	if (hstate_is_gigantic(h))
>  		prep_compound_gigantic_page(page, huge_page_order(h));
>  	prep_new_huge_page(h, page, page_to_nid(page));
> 


-- 
Mike Kravetz

  reply index

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-26 14:50 [PATCH v2 00/19] Free some vmemmap pages of hugetlb page Muchun Song
2020-10-26 14:50 ` [PATCH v2 01/19] mm/memory_hotplug: Move bootmem info registration API to bootmem_info.c Muchun Song
2020-10-26 14:50 ` [PATCH v2 02/19] mm/memory_hotplug: Move {get,put}_page_bootmem() " Muchun Song
2020-10-26 14:50 ` [PATCH v2 03/19] mm/hugetlb: Introduce a new config HUGETLB_PAGE_FREE_VMEMMAP Muchun Song
2020-10-29 10:29   ` Oscar Salvador
2020-10-29 13:34     ` [External] " Muchun Song
2020-10-26 14:50 ` [PATCH v2 04/19] mm/hugetlb: Introduce nr_free_vmemmap_pages in the struct hstate Muchun Song
2020-10-27 22:03   ` Mike Kravetz
2020-10-29 13:26   ` Oscar Salvador
2020-10-29 13:41     ` [External] " Muchun Song
2020-10-26 14:51 ` [PATCH v2 05/19] mm/hugetlb: Introduce pgtable allocation/freeing helpers Muchun Song
2020-10-28  0:32   ` Mike Kravetz [this message]
2020-10-28  7:26     ` [External] " Muchun Song
2020-10-28 23:42       ` Mike Kravetz
2020-11-05 13:23   ` Oscar Salvador
2020-11-05 16:08     ` [External] " Muchun Song
2020-11-06  9:46       ` Oscar Salvador
2020-11-06 16:43         ` Muchun Song
2020-10-26 14:51 ` [PATCH v2 06/19] mm/bootmem_info: Introduce {free,prepare}_vmemmap_page() Muchun Song
2020-10-26 14:51 ` [PATCH v2 07/19] mm/hugetlb: Free the vmemmap pages associated with each hugetlb page Muchun Song
2020-10-26 16:01   ` Matthew Wilcox
2020-10-27  2:58     ` [External] " Muchun Song
2020-10-28 23:42   ` Mike Kravetz
2020-10-29  6:13     ` [External] " Muchun Song
2020-10-29 21:59       ` Mike Kravetz
2020-10-30  2:58         ` Muchun Song
2020-10-26 14:51 ` [PATCH v2 08/19] mm/hugetlb: Defer freeing of hugetlb pages Muchun Song
2020-10-26 14:51 ` [PATCH v2 09/19] mm/hugetlb: Allocate the vmemmap pages associated with each hugetlb page Muchun Song
2020-10-26 14:51 ` [PATCH v2 10/19] mm/hugetlb: Introduce remap_huge_page_pmd_vmemmap helper Muchun Song
2020-10-26 14:51 ` [PATCH v2 11/19] mm/hugetlb: Use PG_slab to indicate split pmd Muchun Song
2020-10-26 14:51 ` [PATCH v2 12/19] mm/hugetlb: Support freeing vmemmap pages of gigantic page Muchun Song
2020-10-26 14:51 ` [PATCH v2 13/19] mm/hugetlb: Add a BUILD_BUG_ON to check if struct page size is a power of two Muchun Song
2020-10-26 14:51 ` [PATCH v2 14/19] mm/hugetlb: Clear PageHWPoison on the non-error memory page Muchun Song
2020-10-26 14:51 ` [PATCH v2 15/19] mm/hugetlb: Flush work when dissolving hugetlb page Muchun Song
2020-10-26 14:51 ` [PATCH v2 16/19] mm/hugetlb: Add a kernel parameter hugetlb_free_vmemmap Muchun Song
2020-10-26 14:51 ` [PATCH v2 17/19] mm/hugetlb: Merge pte to huge pmd only for gigantic page Muchun Song
2020-10-26 14:51 ` [PATCH v2 18/19] mm/hugetlb: Gather discrete indexes of tail page Muchun Song
2020-10-26 14:51 ` [PATCH v2 19/19] mm/hugetlb: Add BUILD_BUG_ON to catch invalid usage of tail struct page Muchun Song
2020-10-26 15:53 ` [PATCH v2 00/19] Free some vmemmap pages of hugetlb page Matthew Wilcox
2020-10-27  2:54   ` [External] " Muchun Song
2020-10-30  9:14 ` Michal Hocko
2020-10-30 10:24   ` [External] " Muchun Song
2020-10-30 15:19     ` Michal Hocko

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=81a7a7f0-fe0e-42e4-8de0-9092b033addc@oracle.com \
    --to=mike.kravetz@oracle.com \
    --cc=akpm@linux-foundation.org \
    --cc=almasrymina@google.com \
    --cc=anshuman.khandual@arm.com \
    --cc=bp@alien8.de \
    --cc=corbet@lwn.net \
    --cc=dave.hansen@linux.intel.com \
    --cc=duanxiongchun@bytedance.com \
    --cc=hpa@zytor.com \
    --cc=jroedel@suse.de \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=luto@kernel.org \
    --cc=mchehab+huawei@kernel.org \
    --cc=mingo@redhat.com \
    --cc=oneukum@suse.com \
    --cc=paulmck@kernel.org \
    --cc=pawan.kumar.gupta@linux.intel.com \
    --cc=peterz@infradead.org \
    --cc=rdunlap@infradead.org \
    --cc=rientjes@google.com \
    --cc=songmuchun@bytedance.com \
    --cc=tglx@linutronix.de \
    --cc=viro@zeniv.linux.org.uk \
    --cc=willy@infradead.org \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Fsdevel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-fsdevel/0 linux-fsdevel/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-fsdevel linux-fsdevel/ https://lore.kernel.org/linux-fsdevel \
		linux-fsdevel@vger.kernel.org
	public-inbox-index linux-fsdevel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-fsdevel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git