| Message ID | 20181115083847.GA11129@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm/swap: use nr_node_ids for avail_lists in swap_info_struct | expand |
On Thu 15-11-18 16:38:47, Aaron Lu wrote: > Since commit 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. I haven't seen any system with a huge nr_node_ids but using kvzalloc is not harmfull. > Cc: Vasily Averin <vvs@virtuozzo.com> > Cc: Michal Hocko <mhocko@suse.com> > Cc: Huang Ying <ying.huang@intel.com> > Signed-off-by: Aaron Lu <aaron.lu@intel.com> Acked-by: Michal Hocko <mhocko@suse.com> > --- > include/linux/swap.h | 11 ++++++++++- > mm/swapfile.c | 3 ++- > 2 files changed, 12 insertions(+), 2 deletions(-) > > diff --git a/include/linux/swap.h b/include/linux/swap.h > index d8a07a4f171d..3d3630b3f63d 100644 > --- a/include/linux/swap.h > +++ b/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 > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 8688ae65ef58..6e06821623f6 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -2812,8 +2812,9 @@ static struct swap_info_struct *alloc_swap_info(void) > 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); > > -- > 2.17.2 >
diff --git a/include/linux/swap.h b/include/linux/swap.h index d8a07a4f171d..3d3630b3f63d 100644 --- a/include/linux/swap.h +++ b/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 diff --git a/mm/swapfile.c b/mm/swapfile.c index 8688ae65ef58..6e06821623f6 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -2812,8 +2812,9 @@ static struct swap_info_struct *alloc_swap_info(void) 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);
Since commit 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. Cc: Vasily Averin <vvs@virtuozzo.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Huang Ying <ying.huang@intel.com> Signed-off-by: Aaron Lu <aaron.lu@intel.com> --- include/linux/swap.h | 11 ++++++++++- mm/swapfile.c | 3 ++- 2 files changed, 12 insertions(+), 2 deletions(-)