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hugetlb: add hugetlb demote page support

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Demote page functionality will split a huge page into a number of huge
pages of a smaller size.  For example, on x86 a 1GB huge page can be
demoted into 512 2M huge pages.  Demotion is done 'in place' by simply
splitting the huge page.

Added '*_for_demote' wrappers for remove_hugetlb_page,
destroy_compound_hugetlb_page and prep_compound_gigantic_page for use by
demote code.

[mike.kravetz@oracle.com: v4]
  Link: https://lkml.kernel.org/r/6ca29b8e-527c-d6ec-900e-e6a43e4f8b73@oracle.com

Link: https://lkml.kernel.org/r/20211007181918.136982-6-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Nghia Le <nghialm78@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mike Kravetz 2021-11-05 13:41:33 -07:00 committed by Linus Torvalds
parent 34d9e35b13
commit 8531fc6f52
1 changed files with 92 additions and 8 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

100
mm/hugetlb.c
View file

@ -1270,7 +1270,7 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
((node = hstate_next_node_to_free(hs, mask)) || 1); \
nr_nodes--)
#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
/* used to demote non-gigantic_huge pages as well */
static void __destroy_compound_gigantic_page(struct page *page,
unsigned int order, bool demote)
{
@ -1293,6 +1293,13 @@ static void __destroy_compound_gigantic_page(struct page *page,
__ClearPageHead(page);
}
static void destroy_compound_hugetlb_page_for_demote(struct page *page,
unsigned int order)
{
__destroy_compound_gigantic_page(page, order, true);
}
#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
static void destroy_compound_gigantic_page(struct page *page,
unsigned int order)
{
@ -1438,6 +1445,12 @@ static void remove_hugetlb_page(struct hstate *h, struct page *page,
__remove_hugetlb_page(h, page, adjust_surplus, false);
}
static void remove_hugetlb_page_for_demote(struct hstate *h, struct page *page,
bool adjust_surplus)
{
__remove_hugetlb_page(h, page, adjust_surplus, true);
}
static void add_hugetlb_page(struct hstate *h, struct page *page,
bool adjust_surplus)
{
@ -1779,6 +1792,12 @@ static bool prep_compound_gigantic_page(struct page *page, unsigned int order)
return __prep_compound_gigantic_page(page, order, false);
}
static bool prep_compound_gigantic_page_for_demote(struct page *page,
unsigned int order)
{
return __prep_compound_gigantic_page(page, order, true);
}
/*
* PageHuge() only returns true for hugetlbfs pages, but not for normal or
* transparent huge pages. See the PageTransHuge() documentation for more
@ -3304,9 +3323,72 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
return 0;
}
static int demote_free_huge_page(struct hstate *h, struct page *page)
{
int i, nid = page_to_nid(page);
struct hstate *target_hstate;
int rc = 0;
target_hstate = size_to_hstate(PAGE_SIZE << h->demote_order);
remove_hugetlb_page_for_demote(h, page, false);
spin_unlock_irq(&hugetlb_lock);
rc = alloc_huge_page_vmemmap(h, page);
if (rc) {
/* Allocation of vmemmmap failed, we can not demote page */
spin_lock_irq(&hugetlb_lock);
set_page_refcounted(page);
add_hugetlb_page(h, page, false);
return rc;
}
/*
* Use destroy_compound_hugetlb_page_for_demote for all huge page
* sizes as it will not ref count pages.
*/
destroy_compound_hugetlb_page_for_demote(page, huge_page_order(h));
/*
* Taking target hstate mutex synchronizes with set_max_huge_pages.
* Without the mutex, pages added to target hstate could be marked
* as surplus.
*
* Note that we already hold h->resize_lock. To prevent deadlock,
* use the convention of always taking larger size hstate mutex first.
*/
mutex_lock(&target_hstate->resize_lock);
for (i = 0; i < pages_per_huge_page(h);
i += pages_per_huge_page(target_hstate)) {
if (hstate_is_gigantic(target_hstate))
prep_compound_gigantic_page_for_demote(page + i,
target_hstate->order);
else
prep_compound_page(page + i, target_hstate->order);
set_page_private(page + i, 0);
set_page_refcounted(page + i);
prep_new_huge_page(target_hstate, page + i, nid);
put_page(page + i);
}
mutex_unlock(&target_hstate->resize_lock);
spin_lock_irq(&hugetlb_lock);
/*
* Not absolutely necessary, but for consistency update max_huge_pages
* based on pool changes for the demoted page.
*/
h->max_huge_pages--;
target_hstate->max_huge_pages += pages_per_huge_page(h);
return rc;
}
static int demote_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed)
__must_hold(&hugetlb_lock)
{
int nr_nodes, node;
struct page *page;
int rc = 0;
lockdep_assert_held(&hugetlb_lock);
@ -3317,9 +3399,15 @@ static int demote_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed)
return -EINVAL; /* internal error */
}
/*
* TODO - demote fucntionality will be added in subsequent patch
*/
for_each_node_mask_to_free(h, nr_nodes, node, nodes_allowed) {
if (!list_empty(&h->hugepage_freelists[node])) {
page = list_entry(h->hugepage_freelists[node].next,
struct page, lru);
rc = demote_free_huge_page(h, page);
break;
}
}
return rc;
}
@ -3554,10 +3642,6 @@ static ssize_t demote_store(struct kobject *kobj,
/*
* Check for available pages to demote each time thorough the
* loop as demote_pool_huge_page will drop hugetlb_lock.
*
* NOTE: demote_pool_huge_page does not yet drop hugetlb_lock
* but will when full demote functionality is added in a later
* patch.
*/
if (nid != NUMA_NO_NODE)
nr_available = h->free_huge_pages_node[nid];