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author | Hugh Dickins <hugh@veritas.com> | 2005-10-29 18:16:40 -0700 |
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committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-10-29 21:40:42 -0700 |
commit | 4c21e2f2441dc5fbb957b030333f5a3f2d02dea7 (patch) | |
tree | 1f76d33bb1d76221c6424bc5fed080a4f91349a6 /mm/swap_state.c | |
parent | b38c6845b695141259019e2b7c0fe6c32a6e720d (diff) | |
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[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/swap_state.c')
-rw-r--r-- | mm/swap_state.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/mm/swap_state.c b/mm/swap_state.c index 132164f..cafc1ed 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -83,7 +83,7 @@ static int __add_to_swap_cache(struct page *page, swp_entry_t entry, page_cache_get(page); SetPageLocked(page); SetPageSwapCache(page); - page->private = entry.val; + set_page_private(page, entry.val); total_swapcache_pages++; pagecache_acct(1); } @@ -126,8 +126,8 @@ void __delete_from_swap_cache(struct page *page) BUG_ON(PageWriteback(page)); BUG_ON(PagePrivate(page)); - radix_tree_delete(&swapper_space.page_tree, page->private); - page->private = 0; + radix_tree_delete(&swapper_space.page_tree, page_private(page)); + set_page_private(page, 0); ClearPageSwapCache(page); total_swapcache_pages--; pagecache_acct(-1); @@ -197,7 +197,7 @@ void delete_from_swap_cache(struct page *page) { swp_entry_t entry; - entry.val = page->private; + entry.val = page_private(page); write_lock_irq(&swapper_space.tree_lock); __delete_from_swap_cache(page); |