[RFC PATCH v2 3/5] hugetlb_cgroup: Add reservation accounting for private mappings
From: Mina Almasry
Date: Thu Aug 08 2019 - 19:14:19 EST
Normally the pointer to the cgroup to uncharge hangs off the struct
page, and gets queried when it's time to free the page. With
hugetlb_cgroup reservations, this is not possible. Because it's possible
for a page to be reserved by one task and actually faulted in by another
task.
The best place to put the hugetlb_cgroup pointer to uncharge for
reservations is in the resv_map. But, because the resv_map has different
semantics for private and shared mappings, the code patch to
charge/uncharge shared and private mappings is different. This patch
implements charging and uncharging for private mappings.
For private mappings, the counter to uncharge is in
resv_map->reservation_counter. On initializing the resv_map this is set
to NULL. On reservation of a region in private mapping, the tasks
hugetlb_cgroup is charged and the hugetlb_cgroup is placed is
resv_map->reservation_counter.
On hugetlb_vm_op_close, we uncharge resv_map->reservation_counter.
---
include/linux/hugetlb.h | 8 ++++++
include/linux/hugetlb_cgroup.h | 11 ++++++++
mm/hugetlb.c | 47 ++++++++++++++++++++++++++++++++--
mm/hugetlb_cgroup.c | 12 ---------
4 files changed, 64 insertions(+), 14 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 6777b3013345d..90b3c928d16c1 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -46,6 +46,14 @@ struct resv_map {
long adds_in_progress;
struct list_head region_cache;
long region_cache_count;
+ #ifdef CONFIG_CGROUP_HUGETLB
+ /*
+ * On private mappings, the counter to uncharge reservations is stored
+ * here. If these fields are 0, then the mapping is shared.
+ */
+ struct page_counter *reservation_counter;
+ unsigned long pages_per_hpage;
+#endif
};
extern struct resv_map *resv_map_alloc(void);
void resv_map_release(struct kref *ref);
diff --git a/include/linux/hugetlb_cgroup.h b/include/linux/hugetlb_cgroup.h
index 0725f809cd2d9..1fdde63a4e775 100644
--- a/include/linux/hugetlb_cgroup.h
+++ b/include/linux/hugetlb_cgroup.h
@@ -25,6 +25,17 @@ struct hugetlb_cgroup;
#define HUGETLB_CGROUP_MIN_ORDER 2
#ifdef CONFIG_CGROUP_HUGETLB
+struct hugetlb_cgroup {
+ struct cgroup_subsys_state css;
+ /*
+ * the counter to account for hugepages from hugetlb.
+ */
+ struct page_counter hugepage[HUGE_MAX_HSTATE];
+ /*
+ * the counter to account for hugepage reservations from hugetlb.
+ */
+ struct page_counter reserved_hugepage[HUGE_MAX_HSTATE];
+};
static inline struct hugetlb_cgroup *hugetlb_cgroup_from_page(struct page *page)
{
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index c153bef42e729..235996aef6618 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -711,6 +711,16 @@ struct resv_map *resv_map_alloc(void)
INIT_LIST_HEAD(&resv_map->regions);
resv_map->adds_in_progress = 0;
+#ifdef CONFIG_CGROUP_HUGETLB
+ /*
+ * Initialize these to 0. On shared mappings, 0's here indicate these
+ * fields don't do cgroup accounting. On private mappings, these will be
+ * re-initialized to the proper values, to indicate that hugetlb cgroup
+ * reservations are to be un-charged from here.
+ */
+ resv_map->reservation_counter = NULL;
+ resv_map->pages_per_hpage = 0;
+#endif
INIT_LIST_HEAD(&resv_map->region_cache);
list_add(&rg->link, &resv_map->region_cache);
@@ -3192,7 +3202,19 @@ static void hugetlb_vm_op_close(struct vm_area_struct *vma)
reserve = (end - start) - region_count(resv, start, end);
- kref_put(&resv->refs, resv_map_release);
+#ifdef CONFIG_CGROUP_HUGETLB
+ /*
+ * Since we check for HPAGE_RESV_OWNER above, this must a private
+ * mapping, and these values should be none-zero, and should point to
+ * the hugetlb_cgroup counter to uncharge for this reservation.
+ */
+ WARN_ON(!resv->reservation_counter);
+ WARN_ON(!resv->pages_per_hpage);
+
+ hugetlb_cgroup_uncharge_counter(
+ resv->reservation_counter,
+ (end - start) * resv->pages_per_hpage);
+#endif
if (reserve) {
/*
@@ -3202,6 +3224,8 @@ static void hugetlb_vm_op_close(struct vm_area_struct *vma)
gbl_reserve = hugepage_subpool_put_pages(spool, reserve);
hugetlb_acct_memory(h, -gbl_reserve);
}
+
+ kref_put(&resv->refs, resv_map_release);
}
static int hugetlb_vm_op_split(struct vm_area_struct *vma, unsigned long addr)
@@ -4516,6 +4540,7 @@ int hugetlb_reserve_pages(struct inode *inode,
struct hstate *h = hstate_inode(inode);
struct hugepage_subpool *spool = subpool_inode(inode);
struct resv_map *resv_map;
+ struct hugetlb_cgroup *h_cg;
long gbl_reserve;
/* This should never happen */
@@ -4549,11 +4574,29 @@ int hugetlb_reserve_pages(struct inode *inode,
chg = region_chg(resv_map, from, to);
} else {
+ /* Private mapping. */
+ chg = to - from;
+
+ if (hugetlb_cgroup_charge_cgroup(
+ hstate_index(h),
+ chg * pages_per_huge_page(h),
+ &h_cg, true)) {
+ return -ENOMEM;
+ }
+
resv_map = resv_map_alloc();
if (!resv_map)
return -ENOMEM;
- chg = to - from;
+#ifdef CONFIG_CGROUP_HUGETLB
+ /*
+ * Since this branch handles private mappings, we attach the
+ * counter to uncharge for this reservation off resv_map.
+ */
+ resv_map->reservation_counter =
+ &h_cg->reserved_hugepage[hstate_index(h)];
+ resv_map->pages_per_hpage = pages_per_huge_page(h);
+#endif
set_vma_resv_map(vma, resv_map);
set_vma_resv_flags(vma, HPAGE_RESV_OWNER);
diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index 119176a0b2ec5..06e99ae1fec81 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -19,18 +19,6 @@
#include <linux/hugetlb.h>
#include <linux/hugetlb_cgroup.h>
-struct hugetlb_cgroup {
- struct cgroup_subsys_state css;
- /*
- * the counter to account for hugepages from hugetlb.
- */
- struct page_counter hugepage[HUGE_MAX_HSTATE];
- /*
- * the counter to account for hugepage reservations from hugetlb.
- */
- struct page_counter reserved_hugepage[HUGE_MAX_HSTATE];
-};
-
#define MEMFILE_PRIVATE(x, val) (((x) << 16) | (val))
#define MEMFILE_IDX(val) (((val) >> 16) & 0xffff)
#define MEMFILE_ATTR(val) ((val) & 0xffff)
--
2.23.0.rc1.153.gdeed80330f-goog