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authorHugh Dickins <hugh@veritas.com>2005-10-30 01:16:40 (GMT)
committerLinus Torvalds <torvalds@g5.osdl.org>2005-10-30 04:40:42 (GMT)
commit4c21e2f2441dc5fbb957b030333f5a3f2d02dea7 (patch)
tree1f76d33bb1d76221c6424bc5fed080a4f91349a6 /mm/page_io.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/page_io.c')
-rw-r--r--mm/page_io.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/mm/page_io.c b/mm/page_io.c
index 330e00d..bb2b0d5 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -91,7 +91,8 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
unlock_page(page);
goto out;
}
- bio = get_swap_bio(GFP_NOIO, page->private, page, end_swap_bio_write);
+ bio = get_swap_bio(GFP_NOIO, page_private(page), page,
+ end_swap_bio_write);
if (bio == NULL) {
set_page_dirty(page);
unlock_page(page);
@@ -115,7 +116,8 @@ int swap_readpage(struct file *file, struct page *page)
BUG_ON(!PageLocked(page));
ClearPageUptodate(page);
- bio = get_swap_bio(GFP_KERNEL, page->private, page, end_swap_bio_read);
+ bio = get_swap_bio(GFP_KERNEL, page_private(page), page,
+ end_swap_bio_read);
if (bio == NULL) {
unlock_page(page);
ret = -ENOMEM;

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