The patch titled
Subject: hugetlb: add hugetlb demote page support
has been added to the -mm tree. Its filename is
hugetlb-add-hugetlb-demote-page-support.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/hugetlb-add-hugetlb-demote-page-support.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/hugetlb-add-hugetlb-demote-page-support.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Subject: hugetlb: add hugetlb demote page support
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_gigantic_page and prep_compound_gigantic_page for use by
demote code.
Link: https://lkml.kernel.org/r/20211001175210.45968-6-mike.kravetz@xxxxxxxxxx
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@xxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 82 ++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 74 insertions(+), 8 deletions(-)
--- a/mm/hugetlb.c~hugetlb-add-hugetlb-demote-page-support
+++ a/mm/hugetlb.c
@@ -1270,7 +1270,7 @@ static int hstate_next_node_to_free(stru
((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_
__ClearPageHead(page);
}
+static void destroy_compound_gigantic_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 h
__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(
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
@@ -3302,9 +3321,54 @@ out:
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_gigantic_page_for_demote for all huge page
+ * sizes as it will not ref count pages.
+ */
+ destroy_compound_gigantic_page_for_demote(page, huge_page_order(h));
+
+ 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);
+ }
+
+ spin_lock_irq(&hugetlb_lock);
+ 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);
@@ -3313,9 +3377,15 @@ static int demote_pool_huge_page(struct
if (!h->demote_order)
return rc;
- /*
- * 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;
}
@@ -3550,10 +3620,6 @@ static ssize_t demote_store(struct kobje
/*
* 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];
_
Patches currently in -mm which might be from mike.kravetz@xxxxxxxxxx are
hugetlb-add-demote-hugetlb-page-sysfs-interfaces.patch
mm-cma-add-cma_pages_valid-to-determine-if-pages-are-in-cma.patch
hugetlb-be-sure-to-free-demoted-cma-pages-to-cma.patch
hugetlb-add-demote-bool-to-gigantic-page-routines.patch
hugetlb-add-hugetlb-demote-page-support.patch
