When I use several fast SSD to do swap, swapper_space.tree_lock is heavily
contended. This makes each swap partition have one address_space to reduce the
lock contention. There is an array of address_space for swap. The swap entry
type is the index to the array.
In my test with 3 SSD, this increases the swapout throughput 20%.
V1->V2: simplify code
Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx>
---
fs/proc/meminfo.c | 4 +--
include/linux/swap.h | 9 ++++----
mm/memcontrol.c | 4 +--
mm/mincore.c | 5 ++--
mm/swap.c | 9 ++++++--
mm/swap_state.c | 57 ++++++++++++++++++++++++++++++++++-----------------
mm/swapfile.c | 5 ++--
mm/util.c | 10 ++++++--
8 files changed, 68 insertions(+), 35 deletions(-)
Index: linux/include/linux/swap.h
===================================================================
--- linux.orig/include/linux/swap.h 2013-01-22 09:13:14.000000000 +0800
+++ linux/include/linux/swap.h 2013-01-22 09:34:44.923011706 +0800
@@ -8,7 +8,7 @@
#include <linux/memcontrol.h>
#include <linux/sched.h>
#include <linux/node.h>
-
+#include <linux/fs.h>
#include <linux/atomic.h>
#include <asm/page.h>
@@ -330,8 +330,9 @@ int generic_swapfile_activate(struct swa
sector_t *);
/* linux/mm/swap_state.c */
-extern struct address_space swapper_space;
-#define total_swapcache_pages swapper_space.nrpages
+extern struct address_space swapper_spaces[];
+#define swap_address_space(entry) (&swapper_spaces[swp_type(entry)])
+extern unsigned long total_swapcache_pages(void);
extern void show_swap_cache_info(void);
extern int add_to_swap(struct page *);
extern int add_to_swap_cache(struct page *, swp_entry_t, gfp_t);
@@ -382,7 +383,7 @@ mem_cgroup_uncharge_swapcache(struct pag
#define nr_swap_pages 0L
#define total_swap_pages 0L
-#define total_swapcache_pages 0UL
+#define total_swapcache_pages() 0UL
#define si_swapinfo(val) \
do { (val)->freeswap = (val)->totalswap = 0; } while (0)
Index: linux/mm/memcontrol.c
===================================================================
--- linux.orig/mm/memcontrol.c 2013-01-22 09:13:14.000000000 +0800
+++ linux/mm/memcontrol.c 2013-01-22 09:29:29.374977700 +0800
@@ -6279,7 +6279,7 @@ static struct page *mc_handle_swap_pte(s
* Because lookup_swap_cache() updates some statistics counter,
* we call find_get_page() with swapper_space directly.
*/
- page = find_get_page(&swapper_space, ent.val);
+ page = find_get_page(swap_address_space(ent), ent.val);
if (do_swap_account)
entry->val = ent.val;
@@ -6320,7 +6320,7 @@ static struct page *mc_handle_file_pte(s
swp_entry_t swap = radix_to_swp_entry(page);
if (do_swap_account)
*entry = swap;
- page = find_get_page(&swapper_space, swap.val);
+ page = find_get_page(swap_address_space(swap), swap.val);
}
#endif
return page;
Index: linux/mm/mincore.c
===================================================================
--- linux.orig/mm/mincore.c 2013-01-22 09:13:14.000000000 +0800
+++ linux/mm/mincore.c 2013-01-22 09:29:29.378977649 +0800
@@ -75,7 +75,7 @@ static unsigned char mincore_page(struct
/* shmem/tmpfs may return swap: account for swapcache page too. */
if (radix_tree_exceptional_entry(page)) {
swp_entry_t swap = radix_to_swp_entry(page);
- page = find_get_page(&swapper_space, swap.val);
+ page = find_get_page(swap_address_space(swap), swap.val);
}
#endif
if (page) {
@@ -135,7 +135,8 @@ static void mincore_pte_range(struct vm_
} else {
#ifdef CONFIG_SWAP
pgoff = entry.val;
- *vec = mincore_page(&swapper_space, pgoff);
+ *vec = mincore_page(swap_address_space(entry),
+ pgoff);
#else
WARN_ON(1);
*vec = 1;
Index: linux/mm/swap.c
===================================================================
--- linux.orig/mm/swap.c 2013-01-22 09:13:14.000000000 +0800
+++ linux/mm/swap.c 2013-01-22 09:29:29.378977649 +0800
@@ -855,9 +855,14 @@ EXPORT_SYMBOL(pagevec_lookup_tag);
void __init swap_setup(void)
{
unsigned long megs = totalram_pages >> (20 - PAGE_SHIFT);
-
#ifdef CONFIG_SWAP
- bdi_init(swapper_space.backing_dev_info);
+ int i;
+
+ for (i = 0; i < MAX_SWAPFILES; i++) {
+ bdi_init(swapper_spaces[i].backing_dev_info);
+ spin_lock_init(&swapper_spaces[i].tree_lock);
+ INIT_LIST_HEAD(&swapper_spaces[i].i_mmap_nonlinear);
+ }
#endif
/* Use a smaller cluster for small-memory machines */
Index: linux/mm/swap_state.c
===================================================================
--- linux.orig/mm/swap_state.c 2013-01-22 09:13:14.000000000 +0800
+++ linux/mm/swap_state.c 2013-01-22 09:29:29.378977649 +0800
@@ -36,12 +36,12 @@ static struct backing_dev_info swap_back
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
};
-struct address_space swapper_space = {
- .page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN),
- .tree_lock = __SPIN_LOCK_UNLOCKED(swapper_space.tree_lock),
- .a_ops = &swap_aops,
- .i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear),
- .backing_dev_info = &swap_backing_dev_info,
+struct address_space swapper_spaces[MAX_SWAPFILES] = {
+ [0 ... MAX_SWAPFILES - 1] = {
+ .page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN),
+ .a_ops = &swap_aops,
+ .backing_dev_info = &swap_backing_dev_info,
+ }
};
#define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0)
@@ -53,9 +53,19 @@ static struct {
unsigned long find_total;
} swap_cache_info;
+unsigned long total_swapcache_pages(void)
+{
+ int i;
+ unsigned long ret = 0;
+
+ for (i = 0; i < MAX_SWAPFILES; i++)
+ ret += swapper_spaces[i].nrpages;
+ return ret;
+}
+
void show_swap_cache_info(void)
{
- printk("%lu pages in swap cache\n", total_swapcache_pages);
+ printk("%lu pages in swap cache\n", total_swapcache_pages());
printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
swap_cache_info.add_total, swap_cache_info.del_total,
swap_cache_info.find_success, swap_cache_info.find_total);
@@ -70,23 +80,26 @@ void show_swap_cache_info(void)
static int __add_to_swap_cache(struct page *page, swp_entry_t entry)
{
int error;
+ struct address_space *address_space;
VM_BUG_ON(!PageLocked(page));
VM_BUG_ON(PageSwapCache(page));
VM_BUG_ON(!PageSwapBacked(page));
page_cache_get(page);
- SetPageSwapCache(page);
set_page_private(page, entry.val);
+ SetPageSwapCache(page);
- spin_lock_irq(&swapper_space.tree_lock);
- error = radix_tree_insert(&swapper_space.page_tree, entry.val, page);
+ address_space = swap_address_space(entry);
+ spin_lock_irq(&address_space->tree_lock);
+ error = radix_tree_insert(&address_space->page_tree,
+ entry.val, page);
if (likely(!error)) {
- total_swapcache_pages++;
+ address_space->nrpages++;
__inc_zone_page_state(page, NR_FILE_PAGES);
INC_CACHE_INFO(add_total);
}
- spin_unlock_irq(&swapper_space.tree_lock);
+ spin_unlock_irq(&address_space->tree_lock);
if (unlikely(error)) {
/*
@@ -122,14 +135,19 @@ int add_to_swap_cache(struct page *page,
*/
void __delete_from_swap_cache(struct page *page)
{
+ swp_entry_t entry;
+ struct address_space *address_space;
+
VM_BUG_ON(!PageLocked(page));
VM_BUG_ON(!PageSwapCache(page));
VM_BUG_ON(PageWriteback(page));
- radix_tree_delete(&swapper_space.page_tree, page_private(page));
+ entry.val = page_private(page);
+ address_space = swap_address_space(entry);
+ radix_tree_delete(&address_space->page_tree, page_private(page));
set_page_private(page, 0);
ClearPageSwapCache(page);
- total_swapcache_pages--;
+ address_space->nrpages--;
__dec_zone_page_state(page, NR_FILE_PAGES);
INC_CACHE_INFO(del_total);
}
@@ -195,12 +213,14 @@ int add_to_swap(struct page *page)
void delete_from_swap_cache(struct page *page)
{
swp_entry_t entry;
+ struct address_space *address_space;
entry.val = page_private(page);
- spin_lock_irq(&swapper_space.tree_lock);
+ address_space = swap_address_space(entry);
+ spin_lock_irq(&address_space->tree_lock);
__delete_from_swap_cache(page);
- spin_unlock_irq(&swapper_space.tree_lock);
+ spin_unlock_irq(&address_space->tree_lock);
swapcache_free(entry, page);
page_cache_release(page);
@@ -263,7 +283,7 @@ struct page * lookup_swap_cache(swp_entr
{
struct page *page;
- page = find_get_page(&swapper_space, entry.val);
+ page = find_get_page(swap_address_space(entry), entry.val);
if (page)
INC_CACHE_INFO(find_success);
@@ -290,7 +310,8 @@ struct page *read_swap_cache_async(swp_e
* called after lookup_swap_cache() failed, re-calling
* that would confuse statistics.
*/
- found_page = find_get_page(&swapper_space, entry.val);
+ found_page = find_get_page(swap_address_space(entry),
+ entry.val);
if (found_page)
break;
Index: linux/mm/swapfile.c
===================================================================
--- linux.orig/mm/swapfile.c 2013-01-22 09:13:14.000000000 +0800
+++ linux/mm/swapfile.c 2013-01-22 09:29:29.378977649 +0800
@@ -79,7 +79,7 @@ __try_to_reclaim_swap(struct swap_info_s
struct page *page;
int ret = 0;
- page = find_get_page(&swapper_space, entry.val);
+ page = find_get_page(swap_address_space(entry), entry.val);
if (!page)
return 0;
/*
@@ -699,7 +699,8 @@ int free_swap_and_cache(swp_entry_t entr
p = swap_info_get(entry);
if (p) {
if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) {
- page = find_get_page(&swapper_space, entry.val);
+ page = find_get_page(swap_address_space(entry),
+ entry.val);
if (page && !trylock_page(page)) {
page_cache_release(page);
page = NULL;
Index: linux/fs/proc/meminfo.c
===================================================================
--- linux.orig/fs/proc/meminfo.c 2013-01-22 09:13:14.000000000 +0800
+++ linux/fs/proc/meminfo.c 2013-01-22 09:29:29.378977649 +0800
@@ -40,7 +40,7 @@ static int meminfo_proc_show(struct seq_
* sysctl_overcommit_ratio / 100) + total_swap_pages;
cached = global_page_state(NR_FILE_PAGES) -
- total_swapcache_pages - i.bufferram;
+ total_swapcache_pages() - i.bufferram;
if (cached < 0)
cached = 0;
@@ -109,7 +109,7 @@ static int meminfo_proc_show(struct seq_
K(i.freeram),
K(i.bufferram),
K(cached),
- K(total_swapcache_pages),
+ K(total_swapcache_pages()),
K(pages[LRU_ACTIVE_ANON] + pages[LRU_ACTIVE_FILE]),
K(pages[LRU_INACTIVE_ANON] + pages[LRU_INACTIVE_FILE]),
K(pages[LRU_ACTIVE_ANON]),
Index: linux/mm/util.c
===================================================================
--- linux.orig/mm/util.c 2013-01-22 09:21:51.000000000 +0800
+++ linux/mm/util.c 2013-01-22 09:30:24.218287858 +0800
@@ -6,6 +6,7 @@
#include <linux/sched.h>
#include <linux/security.h>
#include <linux/swap.h>
+#include <linux/swapops.h>
#include <asm/uaccess.h>
#include "internal.h"
@@ -385,9 +386,12 @@ struct address_space *page_mapping(struc
VM_BUG_ON(PageSlab(page));
#ifdef CONFIG_SWAP
- if (unlikely(PageSwapCache(page)))
- mapping = &swapper_space;
- else
+ if (unlikely(PageSwapCache(page))) {
+ swp_entry_t entry;
+
+ entry.val = page_private(page);
+ mapping = swap_address_space(entry);
+ } else
#endif
if ((unsigned long)mapping & PAGE_MAPPING_ANON)
mapping = NULL;
--
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