diff options
| -rw-r--r-- | Documentation/vm/swap_numa.txt | 69 | ||||
| -rw-r--r-- | include/linux/swap.h | 2 | ||||
| -rw-r--r-- | mm/swapfile.c | 120 |
3 files changed, 164 insertions, 27 deletions
diff --git a/Documentation/vm/swap_numa.txt b/Documentation/vm/swap_numa.txt new file mode 100644 index 000000000000..d5960c9124f5 --- /dev/null +++ b/Documentation/vm/swap_numa.txt @@ -0,0 +1,69 @@ +Automatically bind swap device to numa node +------------------------------------------- + +If the system has more than one swap device and swap device has the node +information, we can make use of this information to decide which swap +device to use in get_swap_pages() to get better performance. + + +How to use this feature +----------------------- + +Swap device has priority and that decides the order of it to be used. To make +use of automatically binding, there is no need to manipulate priority settings +for swap devices. e.g. on a 2 node machine, assume 2 swap devices swapA and +swapB, with swapA attached to node 0 and swapB attached to node 1, are going +to be swapped on. Simply swapping them on by doing: +# swapon /dev/swapA +# swapon /dev/swapB + +Then node 0 will use the two swap devices in the order of swapA then swapB and +node 1 will use the two swap devices in the order of swapB then swapA. Note +that the order of them being swapped on doesn't matter. + +A more complex example on a 4 node machine. Assume 6 swap devices are going to +be swapped on: swapA and swapB are attached to node 0, swapC is attached to +node 1, swapD and swapE are attached to node 2 and swapF is attached to node3. +The way to swap them on is the same as above: +# swapon /dev/swapA +# swapon /dev/swapB +# swapon /dev/swapC +# swapon /dev/swapD +# swapon /dev/swapE +# swapon /dev/swapF + +Then node 0 will use them in the order of: +swapA/swapB -> swapC -> swapD -> swapE -> swapF +swapA and swapB will be used in a round robin mode before any other swap device. + +node 1 will use them in the order of: +swapC -> swapA -> swapB -> swapD -> swapE -> swapF + +node 2 will use them in the order of: +swapD/swapE -> swapA -> swapB -> swapC -> swapF +Similaly, swapD and swapE will be used in a round robin mode before any +other swap devices. + +node 3 will use them in the order of: +swapF -> swapA -> swapB -> swapC -> swapD -> swapE + + +Implementation details +---------------------- + +The current code uses a priority based list, swap_avail_list, to decide +which swap device to use and if multiple swap devices share the same +priority, they are used round robin. This change here replaces the single +global swap_avail_list with a per-numa-node list, i.e. for each numa node, +it sees its own priority based list of available swap devices. Swap +device's priority can be promoted on its matching node's swap_avail_list. + +The current swap device's priority is set as: user can set a >=0 value, +or the system will pick one starting from -1 then downwards. The priority +value in the swap_avail_list is the negated value of the swap device's +due to plist being sorted from low to high. The new policy doesn't change +the semantics for priority >=0 cases, the previous starting from -1 then +downwards now becomes starting from -2 then downwards and -1 is reserved +as the promoted value. So if multiple swap devices are attached to the same +node, they will all be promoted to priority -1 on that node's plist and will +be used round robin before any other swap devices. diff --git a/include/linux/swap.h b/include/linux/swap.h index 9c4ae6f14eea..8bf3487fb204 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -212,7 +212,7 @@ 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_list; /* entry in swap_avail_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 */ diff --git a/mm/swapfile.c b/mm/swapfile.c index 4f8b3e08a547..d483278ee35b 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -60,7 +60,7 @@ atomic_long_t nr_swap_pages; EXPORT_SYMBOL_GPL(nr_swap_pages); /* protected with swap_lock. reading in vm_swap_full() doesn't need lock */ long total_swap_pages; -static int least_priority; +static int least_priority = -1; static const char Bad_file[] = "Bad swap file entry "; static const char Unused_file[] = "Unused swap file entry "; @@ -85,7 +85,7 @@ PLIST_HEAD(swap_active_head); * is held and the locking order requires swap_lock to be taken * before any swap_info_struct->lock. */ -static PLIST_HEAD(swap_avail_head); +struct plist_head *swap_avail_heads; static DEFINE_SPINLOCK(swap_avail_lock); struct swap_info_struct *swap_info[MAX_SWAPFILES]; @@ -592,6 +592,21 @@ new_cluster: return found_free; } +static void __del_from_avail_list(struct swap_info_struct *p) +{ + int nid; + + for_each_node(nid) + plist_del(&p->avail_lists[nid], &swap_avail_heads[nid]); +} + +static void del_from_avail_list(struct swap_info_struct *p) +{ + spin_lock(&swap_avail_lock); + __del_from_avail_list(p); + spin_unlock(&swap_avail_lock); +} + static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset, unsigned int nr_entries) { @@ -605,12 +620,22 @@ static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset, if (si->inuse_pages == si->pages) { si->lowest_bit = si->max; si->highest_bit = 0; - spin_lock(&swap_avail_lock); - plist_del(&si->avail_list, &swap_avail_head); - spin_unlock(&swap_avail_lock); + del_from_avail_list(si); } } +static void add_to_avail_list(struct swap_info_struct *p) +{ + int nid; + + spin_lock(&swap_avail_lock); + for_each_node(nid) { + WARN_ON(!plist_node_empty(&p->avail_lists[nid])); + plist_add(&p->avail_lists[nid], &swap_avail_heads[nid]); + } + spin_unlock(&swap_avail_lock); +} + static void swap_range_free(struct swap_info_struct *si, unsigned long offset, unsigned int nr_entries) { @@ -623,13 +648,8 @@ static void swap_range_free(struct swap_info_struct *si, unsigned long offset, bool was_full = !si->highest_bit; si->highest_bit = end; - if (was_full && (si->flags & SWP_WRITEOK)) { - spin_lock(&swap_avail_lock); - WARN_ON(!plist_node_empty(&si->avail_list)); - if (plist_node_empty(&si->avail_list)) - plist_add(&si->avail_list, &swap_avail_head); - spin_unlock(&swap_avail_lock); - } + if (was_full && (si->flags & SWP_WRITEOK)) + add_to_avail_list(si); } atomic_long_add(nr_entries, &nr_swap_pages); si->inuse_pages -= nr_entries; @@ -910,6 +930,7 @@ int get_swap_pages(int n_goal, bool cluster, swp_entry_t swp_entries[]) struct swap_info_struct *si, *next; long avail_pgs; int n_ret = 0; + int node; /* Only single cluster request supported */ WARN_ON_ONCE(n_goal > 1 && cluster); @@ -929,14 +950,15 @@ int get_swap_pages(int n_goal, bool cluster, swp_entry_t swp_entries[]) spin_lock(&swap_avail_lock); start_over: - plist_for_each_entry_safe(si, next, &swap_avail_head, avail_list) { + node = numa_node_id(); + plist_for_each_entry_safe(si, next, &swap_avail_heads[node], avail_lists[node]) { /* requeue si to after same-priority siblings */ - plist_requeue(&si->avail_list, &swap_avail_head); + plist_requeue(&si->avail_lists[node], &swap_avail_heads[node]); spin_unlock(&swap_avail_lock); spin_lock(&si->lock); if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) { spin_lock(&swap_avail_lock); - if (plist_node_empty(&si->avail_list)) { + if (plist_node_empty(&si->avail_lists[node])) { spin_unlock(&si->lock); goto nextsi; } @@ -946,7 +968,7 @@ start_over: WARN(!(si->flags & SWP_WRITEOK), "swap_info %d in list but !SWP_WRITEOK\n", si->type); - plist_del(&si->avail_list, &swap_avail_head); + __del_from_avail_list(si); spin_unlock(&si->lock); goto nextsi; } @@ -975,7 +997,7 @@ nextsi: * swap_avail_head list then try it, otherwise start over * if we have not gotten any slots. */ - if (plist_node_empty(&next->avail_list)) + if (plist_node_empty(&next->avail_lists[node])) goto start_over; } @@ -2410,10 +2432,24 @@ static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span) return generic_swapfile_activate(sis, swap_file, span); } +static int swap_node(struct swap_info_struct *p) +{ + struct block_device *bdev; + + if (p->bdev) + bdev = p->bdev; + else + bdev = p->swap_file->f_inode->i_sb->s_bdev; + + return bdev ? bdev->bd_disk->node_id : NUMA_NO_NODE; +} + static void _enable_swap_info(struct swap_info_struct *p, int prio, unsigned char *swap_map, struct swap_cluster_info *cluster_info) { + int i; + if (prio >= 0) p->prio = prio; else @@ -2423,7 +2459,16 @@ static void _enable_swap_info(struct swap_info_struct *p, int prio, * low-to-high, while swap ordering is high-to-low */ p->list.prio = -p->prio; - p->avail_list.prio = -p->prio; + for_each_node(i) { + if (p->prio >= 0) + p->avail_lists[i].prio = -p->prio; + else { + if (swap_node(p) == i) + p->avail_lists[i].prio = 1; + else + p->avail_lists[i].prio = -p->prio; + } + } p->swap_map = swap_map; p->cluster_info = cluster_info; p->flags |= SWP_WRITEOK; @@ -2442,9 +2487,7 @@ static void _enable_swap_info(struct swap_info_struct *p, int prio, * swap_info_struct. */ plist_add(&p->list, &swap_active_head); - spin_lock(&swap_avail_lock); - plist_add(&p->avail_list, &swap_avail_head); - spin_unlock(&swap_avail_lock); + add_to_avail_list(p); } static void enable_swap_info(struct swap_info_struct *p, int prio, @@ -2529,17 +2572,19 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) spin_unlock(&swap_lock); goto out_dput; } - spin_lock(&swap_avail_lock); - plist_del(&p->avail_list, &swap_avail_head); - spin_unlock(&swap_avail_lock); + del_from_avail_list(p); spin_lock(&p->lock); if (p->prio < 0) { struct swap_info_struct *si = p; + int nid; plist_for_each_entry_continue(si, &swap_active_head, list) { si->prio++; si->list.prio--; - si->avail_list.prio--; + for_each_node(nid) { + if (si->avail_lists[nid].prio != 1) + si->avail_lists[nid].prio--; + } } least_priority++; } @@ -2783,6 +2828,7 @@ static struct swap_info_struct *alloc_swap_info(void) { struct swap_info_struct *p; unsigned int type; + int i; p = kzalloc(sizeof(*p), GFP_KERNEL); if (!p) @@ -2818,7 +2864,8 @@ static struct swap_info_struct *alloc_swap_info(void) } INIT_LIST_HEAD(&p->first_swap_extent.list); plist_node_init(&p->list, 0); - plist_node_init(&p->avail_list, 0); + for_each_node(i) + plist_node_init(&p->avail_lists[i], 0); p->flags = SWP_USED; spin_unlock(&swap_lock); spin_lock_init(&p->lock); @@ -3060,6 +3107,9 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) if (!capable(CAP_SYS_ADMIN)) return -EPERM; + if (!swap_avail_heads) + return -ENOMEM; + p = alloc_swap_info(); if (IS_ERR(p)) return PTR_ERR(p); @@ -3645,3 +3695,21 @@ static void free_swap_count_continuations(struct swap_info_struct *si) } } } + +static int __init swapfile_init(void) +{ + int nid; + + swap_avail_heads = kmalloc_array(nr_node_ids, sizeof(struct plist_head), + GFP_KERNEL); + if (!swap_avail_heads) { + pr_emerg("Not enough memory for swap heads, swap is disabled\n"); + return -ENOMEM; + } + + for_each_node(nid) + plist_head_init(&swap_avail_heads[nid]); + + return 0; +} +subsys_initcall(swapfile_init); |