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Subject[RFC PATCH v2 29/30] mm: thp: use cma reservation for pud thp allocation.
Date
From: Zi Yan <ziy@nvidia.com>

Sharing hugepage_cma reservation with hugetlb for pud thp allocaiton.
The reserved cma regions still can be used for moveable page allocations.

During 1GB page split, all subpages are cleared from the CMA bitmap,
since they are no more 1GB pages and will be freed via the normal path
instead of cma_release().

Signed-off-by: Zi Yan <ziy@nvidia.com>
---
include/linux/cma.h | 3 +++
include/linux/huge_mm.h | 10 ++++++++++
mm/cma.c | 31 +++++++++++++++++++++++++++++++
mm/huge_memory.c | 34 ++++++++++++++++++++++++++++++++++
mm/hugetlb.c | 21 +--------------------
mm/mempolicy.c | 14 +++++++++++++-
mm/page_alloc.c | 29 +++++++++++++++++++++++++++++
7 files changed, 121 insertions(+), 21 deletions(-)

diff --git a/include/linux/cma.h b/include/linux/cma.h
index 9989d580c2a7..c299b62b3a7a 100644
--- a/include/linux/cma.h
+++ b/include/linux/cma.h
@@ -48,6 +48,9 @@ extern struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
bool no_warn);
extern bool cma_release(struct cma *cma, const struct page *pages, unsigned int count);

+extern bool cma_clear_bitmap_if_in_range(struct cma *cma, const struct page *page,
+ unsigned int count);
+
extern int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data);

extern void cma_reserve(int min_order, unsigned long requested_size,
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 0d0f9cf25aeb..163b244d9acd 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -24,6 +24,8 @@ extern struct page *follow_trans_huge_pud(struct vm_area_struct *vma,
unsigned long addr,
pud_t *pud,
unsigned int flags);
+extern struct page *alloc_thp_pud_page(int nid);
+extern bool free_thp_pud_page(struct page *page, int order);
#else
static inline void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
{
@@ -43,6 +45,14 @@ struct page *follow_trans_huge_pud(struct vm_area_struct *vma,
{
return NULL;
}
+struct page *alloc_thp_pud_page(int nid)
+{
+ return NULL;
+}
+extern bool free_thp_pud_page(struct page *page, int order);
+{
+ return false;
+}
#endif

extern vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd);
diff --git a/mm/cma.c b/mm/cma.c
index 1a9d997fa5ab..c595aad61f58 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -532,6 +532,37 @@ bool cma_release(struct cma *cma, const struct page *pages, unsigned int count)
return true;
}

+/**
+ * cma_clear_bitmap_if_in_range() - clear bitmap for a given page
+ * @cma: Contiguous memory region for which the allocation is performed.
+ * @pages: Allocated pages.
+ * @count: Number of allocated pages.
+ *
+ * This function clears bitmap of memory allocated by cma_alloc().
+ * It returns false when provided pages do not belong to contiguous area and
+ * true otherwise.
+ */
+bool cma_clear_bitmap_if_in_range(struct cma *cma, const struct page *pages,
+ unsigned int count)
+{
+ unsigned long pfn;
+
+ if (!cma || !pages)
+ return false;
+
+ pfn = page_to_pfn(pages);
+
+ if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
+ return false;
+
+ if (pfn + count > cma->base_pfn + cma->count)
+ return false;
+
+ cma_clear_bitmap(cma, pfn, count);
+
+ return true;
+}
+
int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data)
{
int i;
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 20ecffc27396..910e51f35910 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -33,6 +33,7 @@
#include <linux/oom.h>
#include <linux/numa.h>
#include <linux/page_owner.h>
+#include <linux/cma.h>

#include <asm/tlb.h>
#include <asm/pgalloc.h>
@@ -62,6 +63,10 @@ static struct shrinker deferred_split_shrinker;
static atomic_t huge_zero_refcount;
struct page *huge_zero_page __read_mostly;

+#ifdef CONFIG_CMA
+extern struct cma *hugepage_cma[MAX_NUMNODES];
+#endif
+
bool transparent_hugepage_enabled(struct vm_area_struct *vma)
{
/* The addr is used to check if the vma size fits */
@@ -2498,6 +2503,17 @@ static void __split_huge_pud_page(struct page *page, struct list_head *list,
/* no file-back page support yet */
VM_BUG_ON(!PageAnon(page));

+ /*
+ * clear cma bitmap when we split pud page so the subpages can be freed
+ * as normal pages
+ */
+ if (IS_ENABLED(CONFIG_CMA)) {
+ struct cma *cma = hugepage_cma[page_to_nid(head)];
+
+ VM_BUG_ON(!cma_clear_bitmap_if_in_range(cma, head,
+ thp_nr_pages(head)));
+ }
+
for (i = HPAGE_PUD_NR - HPAGE_PMD_NR; i >= 1; i -= HPAGE_PMD_NR)
__split_huge_pud_page_tail(head, i, lruvec, list);

@@ -3732,3 +3748,21 @@ void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
update_mmu_cache_pmd(vma, address, pvmw->pmd);
}
#endif
+
+struct page *alloc_thp_pud_page(int nid)
+{
+ struct page *page = NULL;
+#ifdef CONFIG_CMA
+ page = cma_alloc(hugepage_cma[nid], HPAGE_PUD_NR, HPAGE_PUD_ORDER, true);
+#endif
+ return page;
+}
+
+bool free_thp_pud_page(struct page *page, int order)
+{
+ bool ret = false;
+#ifdef CONFIG_CMA
+ ret = cma_release(hugepage_cma[page_to_nid(page)], page, 1<<order);
+#endif
+ return ret;
+}
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 871f1c315c48..0282110c72b5 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1200,26 +1200,7 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
nr_nodes--)

#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
-static void destroy_compound_gigantic_page(struct page *page,
- unsigned int order)
-{
- int i;
- int nr_pages = 1 << order;
- struct page *p = page + 1;
-
- atomic_set(compound_mapcount_ptr(page), 0);
- if (hpage_pincount_available(page))
- atomic_set(compound_pincount_ptr(page), 0);
-
- for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
- clear_compound_head(p);
- set_page_refcounted(p);
- }
-
- set_compound_order(page, 0);
- __ClearPageHead(page);
-}
-
+extern void destroy_compound_gigantic_page(struct page *page, unsigned int order);
static void free_gigantic_page(struct page *page, unsigned int order)
{
/*
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 731a7710395f..dc3d6371195f 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2143,7 +2143,12 @@ static struct page *alloc_page_interleave(gfp_t gfp, unsigned order,
{
struct page *page;

- page = __alloc_pages(gfp, order, nid);
+ if (order == HPAGE_PUD_ORDER) {
+ page = alloc_thp_pud_page(nid);
+ if (page && (gfp & __GFP_COMP))
+ prep_compound_page(page, order);
+ } else
+ page = __alloc_pages(gfp, order, nid);
/* skip NUMA_INTERLEAVE_HIT counter update if numa stats is disabled */
if (!static_branch_likely(&vm_numa_stat_key))
return page;
@@ -2217,6 +2222,13 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
nmask = policy_nodemask(gfp, pol);
if (!nmask || node_isset(hpage_node, *nmask)) {
mpol_cond_put(pol);
+
+ if (order == HPAGE_PUD_ORDER) {
+ page = alloc_thp_pud_page(hpage_node);
+ if (page && (gfp & __GFP_COMP))
+ prep_compound_page(page, order);
+ goto out;
+ }
/*
* First, try to allocate THP only on local node, but
* don't reclaim unnecessarily, just compact.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6bdb38a8fb48..5251ecb30465 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1481,6 +1481,25 @@ void __meminit reserve_bootmem_region(phys_addr_t start, phys_addr_t end)
}
}

+void destroy_compound_gigantic_page(struct page *page, unsigned int order)
+{
+ int i;
+ int nr_pages = 1 << order;
+ struct page *p = page + 1;
+
+ atomic_set(compound_mapcount_ptr(page), 0);
+ if (hpage_pincount_available(page))
+ atomic_set(compound_pincount_ptr(page), 0);
+
+ for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
+ clear_compound_head(p);
+ set_page_refcounted(p);
+ }
+
+ set_compound_order(page, 0);
+ __ClearPageHead(page);
+}
+
static void __free_pages_ok(struct page *page, unsigned int order)
{
unsigned long flags;
@@ -1490,6 +1509,16 @@ static void __free_pages_ok(struct page *page, unsigned int order)
if (!free_pages_prepare(page, order, true))
return;

+ if (order == HPAGE_PUD_ORDER) {
+ bool thp_pud_page_freed = false;
+
+ destroy_compound_gigantic_page(page, order);
+ set_page_refcounted(page);
+ thp_pud_page_freed = free_thp_pud_page(page, order);
+ VM_BUG_ON_PAGE(!thp_pud_page_freed, page);
+ return;
+ }
+
migratetype = get_pfnblock_migratetype(page, pfn);
local_irq_save(flags);
__count_vm_events(PGFREE, 1 << order);
--
2.28.0
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