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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/page_alloc.c | |
parent | b38c6845b695141259019e2b7c0fe6c32a6e720d (diff) | |
download | linux-stable-4c21e2f2441dc5fbb957b030333f5a3f2d02dea7.tar.gz linux-stable-4c21e2f2441dc5fbb957b030333f5a3f2d02dea7.tar.bz2 linux-stable-4c21e2f2441dc5fbb957b030333f5a3f2d02dea7.zip |
[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_alloc.c')
-rw-r--r-- | mm/page_alloc.c | 16 |
1 files changed, 8 insertions, 8 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 0541288ebf4b..a2995a5d012c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -154,7 +154,7 @@ static void prep_compound_page(struct page *page, unsigned long order) struct page *p = page + i; SetPageCompound(p); - p->private = (unsigned long)page; + set_page_private(p, (unsigned long)page); } } @@ -174,7 +174,7 @@ static void destroy_compound_page(struct page *page, unsigned long order) if (!PageCompound(p)) bad_page(__FUNCTION__, page); - if (p->private != (unsigned long)page) + if (page_private(p) != (unsigned long)page) bad_page(__FUNCTION__, page); ClearPageCompound(p); } @@ -187,18 +187,18 @@ static void destroy_compound_page(struct page *page, unsigned long order) * So, we don't need atomic page->flags operations here. */ static inline unsigned long page_order(struct page *page) { - return page->private; + return page_private(page); } static inline void set_page_order(struct page *page, int order) { - page->private = order; + set_page_private(page, order); __SetPagePrivate(page); } static inline void rmv_page_order(struct page *page) { __ClearPagePrivate(page); - page->private = 0; + set_page_private(page, 0); } /* @@ -238,7 +238,7 @@ __find_combined_index(unsigned long page_idx, unsigned int order) * (a) the buddy is free && * (b) the buddy is on the buddy system && * (c) a page and its buddy have the same order. - * for recording page's order, we use page->private and PG_private. + * for recording page's order, we use page_private(page) and PG_private. * */ static inline int page_is_buddy(struct page *page, int order) @@ -264,7 +264,7 @@ static inline int page_is_buddy(struct page *page, int order) * parts of the VM system. * At each level, we keep a list of pages, which are heads of continuous * free pages of length of (1 << order) and marked with PG_Private.Page's - * order is recorded in page->private field. + * order is recorded in page_private(page) field. * So when we are allocating or freeing one, we can derive the state of the * other. That is, if we allocate a small block, and both were * free, the remainder of the region must be split into blocks. @@ -463,7 +463,7 @@ static void prep_new_page(struct page *page, int order) page->flags &= ~(1 << PG_uptodate | 1 << PG_error | 1 << PG_referenced | 1 << PG_arch_1 | 1 << PG_checked | 1 << PG_mappedtodisk); - page->private = 0; + set_page_private(page, 0); set_page_refs(page, order); kernel_map_pages(page, 1 << order, 1); } |