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authorHugh Dickins <hugh@veritas.com>2005-10-29 21:16:40 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2005-10-30 00:40:42 -0400
commit4c21e2f2441dc5fbb957b030333f5a3f2d02dea7 (patch)
tree1f76d33bb1d76221c6424bc5fed080a4f91349a6 /mm/swapfile.c
parentb38c6845b695141259019e2b7c0fe6c32a6e720d (diff)
[PATCH] mm: split page table lock
Christoph Lameter demonstrated very poor scalability on the SGI 512-way, with a many-threaded application which concurrently initializes different parts of a large anonymous area. This patch corrects that, by using a separate spinlock per page table page, to guard the page table entries in that page, instead of using the mm's single page_table_lock. (But even then, page_table_lock is still used to guard page table allocation, and anon_vma allocation.) In this implementation, the spinlock is tucked inside the struct page of the page table page: with a BUILD_BUG_ON in case it overflows - which it would in the case of 32-bit PA-RISC with spinlock debugging enabled. Splitting the lock is not quite for free: another cacheline access. Ideally, I suppose we would use split ptlock only for multi-threaded processes on multi-cpu machines; but deciding that dynamically would have its own costs. So for now enable it by config, at some number of cpus - since the Kconfig language doesn't support inequalities, let preprocessor compare that with NR_CPUS. But I don't think it's worth being user-configurable: for good testing of both split and unsplit configs, split now at 4 cpus, and perhaps change that to 8 later. There is a benefit even for singly threaded processes: kswapd can be attacking one part of the mm while another part is busy faulting. Signed-off-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm/swapfile.c')
-rw-r--r--mm/swapfile.c12
1 files changed, 6 insertions, 6 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 510f0039b00..8970c0b7419 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -61,7 +61,7 @@ void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
61 swp_entry_t entry; 61 swp_entry_t entry;
62 62
63 down_read(&swap_unplug_sem); 63 down_read(&swap_unplug_sem);
64 entry.val = page->private; 64 entry.val = page_private(page);
65 if (PageSwapCache(page)) { 65 if (PageSwapCache(page)) {
66 struct block_device *bdev = swap_info[swp_type(entry)].bdev; 66 struct block_device *bdev = swap_info[swp_type(entry)].bdev;
67 struct backing_dev_info *bdi; 67 struct backing_dev_info *bdi;
@@ -69,8 +69,8 @@ void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
69 /* 69 /*
70 * If the page is removed from swapcache from under us (with a 70 * If the page is removed from swapcache from under us (with a
71 * racy try_to_unuse/swapoff) we need an additional reference 71 * racy try_to_unuse/swapoff) we need an additional reference
72 * count to avoid reading garbage from page->private above. If 72 * count to avoid reading garbage from page_private(page) above.
73 * the WARN_ON triggers during a swapoff it maybe the race 73 * If the WARN_ON triggers during a swapoff it maybe the race
74 * condition and it's harmless. However if it triggers without 74 * condition and it's harmless. However if it triggers without
75 * swapoff it signals a problem. 75 * swapoff it signals a problem.
76 */ 76 */
@@ -294,7 +294,7 @@ static inline int page_swapcount(struct page *page)
294 struct swap_info_struct *p; 294 struct swap_info_struct *p;
295 swp_entry_t entry; 295 swp_entry_t entry;
296 296
297 entry.val = page->private; 297 entry.val = page_private(page);
298 p = swap_info_get(entry); 298 p = swap_info_get(entry);
299 if (p) { 299 if (p) {
300 /* Subtract the 1 for the swap cache itself */ 300 /* Subtract the 1 for the swap cache itself */
@@ -339,7 +339,7 @@ int remove_exclusive_swap_page(struct page *page)
339 if (page_count(page) != 2) /* 2: us + cache */ 339 if (page_count(page) != 2) /* 2: us + cache */
340 return 0; 340 return 0;
341 341
342 entry.val = page->private; 342 entry.val = page_private(page);
343 p = swap_info_get(entry); 343 p = swap_info_get(entry);
344 if (!p) 344 if (!p)
345 return 0; 345 return 0;
@@ -1042,7 +1042,7 @@ int page_queue_congested(struct page *page)
1042 BUG_ON(!PageLocked(page)); /* It pins the swap_info_struct */ 1042 BUG_ON(!PageLocked(page)); /* It pins the swap_info_struct */
1043 1043
1044 if (PageSwapCache(page)) { 1044 if (PageSwapCache(page)) {
1045 swp_entry_t entry = { .val = page->private }; 1045 swp_entry_t entry = { .val = page_private(page) };
1046 struct swap_info_struct *sis; 1046 struct swap_info_struct *sis;
1047 1047
1048 sis = get_swap_info_struct(swp_type(entry)); 1048 sis = get_swap_info_struct(swp_type(entry));