The patch titled
Subject: mm/swap: use nr_node_ids for avail_lists in swap_info_struct
has been added to the -mm tree. Its filename is
mm-swap-use-nr_node_ids-for-avail_lists-in-swap_info_struct.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-swap-use-nr_node_ids-for-avail_lists-in-swap_info_struct.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-swap-use-nr_node_ids-for-avail_lists-in-swap_info_struct.patch
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------------------------------------------------------
From: Aaron Lu <aaron.lu@xxxxxxxxx>
Subject: mm/swap: use nr_node_ids for avail_lists in swap_info_struct
Since a2468cc9bfdf ("swap: choose swap device according to numa node"),
avail_lists field of swap_info_struct is changed to an array with
MAX_NUMNODES elements. This made swap_info_struct size increased to 40KiB
and needs an order-4 page to hold it.
This is not optimal in that:
1 Most systems have way less than MAX_NUMNODES(1024) nodes so it
is a waste of memory;
2 It could cause swapon failure if the swap device is swapped on
after system has been running for a while, due to no order-4
page is available as pointed out by Vasily Averin.
Solve the above two issues by using nr_node_ids(which is the actual
possible node number the running system has) for avail_lists instead of
MAX_NUMNODES.
nr_node_ids is unknown at compile time so can't be directly used when
declaring this array. What I did here is to declare avail_lists as zero
element array and allocate space for it when allocating space for
swap_info_struct. The reason why keep using array but not pointer is
plist_for_each_entry needs the field to be part of the struct, so pointer
will not work.
This patch is on top of Vasily Averin's fix commit. I think the use of
kvzalloc for swap_info_struct is still needed in case nr_node_ids is
really big on some systems.
Link: http://lkml.kernel.org/r/20181115083847.GA11129@xxxxxxxxx
Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Vasily Averin <vvs@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/swap.h | 11 ++++++++++-
mm/swapfile.c | 3 ++-
2 files changed, 12 insertions(+), 2 deletions(-)
--- a/include/linux/swap.h~mm-swap-use-nr_node_ids-for-avail_lists-in-swap_info_struct
+++ a/include/linux/swap.h
@@ -233,7 +233,6 @@ struct swap_info_struct {
unsigned long flags; /* SWP_USED etc: see above */
signed short prio; /* swap priority of this type */
struct plist_node list; /* entry in swap_active_head */
- struct plist_node avail_lists[MAX_NUMNODES];/* entry in swap_avail_heads */
signed char type; /* strange name for an index */
unsigned int max; /* extent of the swap_map */
unsigned char *swap_map; /* vmalloc'ed array of usage counts */
@@ -274,6 +273,16 @@ struct swap_info_struct {
*/
struct work_struct discard_work; /* discard worker */
struct swap_cluster_list discard_clusters; /* discard clusters list */
+ struct plist_node avail_lists[0]; /*
+ * entries in swap_avail_heads, one
+ * entry per node.
+ * Must be last as the number of the
+ * array is nr_node_ids, which is not
+ * a fixed value so have to allocate
+ * dynamically.
+ * And it has to be an array so that
+ * plist_for_each_* can work.
+ */
};
#ifdef CONFIG_64BIT
--- a/mm/swapfile.c~mm-swap-use-nr_node_ids-for-avail_lists-in-swap_info_struct
+++ a/mm/swapfile.c
@@ -2812,8 +2812,9 @@ static struct swap_info_struct *alloc_sw
struct swap_info_struct *p;
unsigned int type;
int i;
+ int size = sizeof(*p) + nr_node_ids * sizeof(struct plist_node);
- p = kvzalloc(sizeof(*p), GFP_KERNEL);
+ p = kvzalloc(size, GFP_KERNEL);
if (!p)
return ERR_PTR(-ENOMEM);
_
Patches currently in -mm which might be from aaron.lu@xxxxxxxxx are
mm-swap-use-nr_node_ids-for-avail_lists-in-swap_info_struct.patch
