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authorHugh Dickins <hugh@veritas.com>2005-10-29 18:16:40 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-10-29 21:40:42 -0700
commit4c21e2f2441dc5fbb957b030333f5a3f2d02dea7 (patch)
tree1f76d33bb1d76221c6424bc5fed080a4f91349a6 /mm/rmap.c
parentb38c6845b695141259019e2b7c0fe6c32a6e720d (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/rmap.c')
-rw-r--r--mm/rmap.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index a84bdfe582c..a33e779d1bd 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -274,7 +274,7 @@ pte_t *page_check_address(struct page *page, struct mm_struct *mm,
return NULL;
}
- ptl = &mm->page_table_lock;
+ ptl = pte_lockptr(mm, pmd);
spin_lock(ptl);
if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
*ptlp = ptl;
@@ -550,7 +550,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
update_hiwater_rss(mm);
if (PageAnon(page)) {
- swp_entry_t entry = { .val = page->private };
+ swp_entry_t entry = { .val = page_private(page) };
/*
* Store the swap location in the pte.
* See handle_pte_fault() ...