[patch] hugepage allocator cleanup

Nick Piggin
2006-01-25T09:11:03Z

Hi,

This is a slight rework of the mechanism for allocating "fresh" hugepages.
Comments?

Thanks,
Nick

--
Insert "fresh" huge pages into the hugepage allocator by the same
means as they are freed back into it. This reduces code size and
allows enqueue_huge_page to be inlined into the hugepage free
fastpath.

Eliminate occurances of hugepages on the free list with non-zero
refcount. This can allow stricter refcount checks in future. Also
required for lockless pagecache.

Signed-off-by: Nick Piggin <npiggin@suse.de>

Index: linux-2.6/mm/hugetlb.c
===================================================================
--- linux-2.6.orig/mm/hugetlb.c
+++ linux-2.6/mm/hugetlb.c
@@ -64,7 +64,7 @@ static struct page *dequeue_huge_page(st
return page;
}

-static struct page *alloc_fresh_huge_page(void)
+static int alloc_fresh_huge_page(void)
{
static int nid = 0;
struct page *page;
@@ -72,12 +72,15 @@ static struct page *alloc_fresh_huge_pag
HUGETLB_PAGE_ORDER);
nid = (nid + 1) % num_online_nodes();
if (page) {
+ page[1].mapping = (void *)free_huge_page;
spin_lock(&hugetlb_lock);
nr_huge_pages++;
nr_huge_pages_node[page_to_nid(page)]++;
spin_unlock(&hugetlb_lock);
+ put_page(page); /* free it into the hugepage allocator */
+ return 1;
}
- return page;
+ return 0;
}

void free_huge_page(struct page *page)
@@ -85,7 +88,6 @@ void free_huge_page(struct page *page)
BUG_ON(page_count(page));

INIT_LIST_HEAD(&page->lru);
- page[1].mapping = NULL;

spin_lock(&hugetlb_lock);
enqueue_huge_page(page);
@@ -105,7 +107,6 @@ struct page *alloc_huge_page(struct vm_a
}
spin_unlock(&hugetlb_lock);
set_page_count(page, 1);
- page[1].mapping = (void *)free_huge_page;
for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); ++i)
clear_highpage(&page[i]);
return page;
@@ -114,7 +115,6 @@ struct page *alloc_huge_page(struct vm_a
static int __init hugetlb_init(void)
{
unsigned long i;
- struct page *page;

if (HPAGE_SHIFT == 0)
return 0;
@@ -123,12 +123,8 @@ static int __init hugetlb_init(void)
INIT_LIST_HEAD(&hugepage_freelists[i]);

for (i = 0; i < max_huge_pages; ++i) {
- page = alloc_fresh_huge_page();
- if (!page)
+ if (!alloc_fresh_huge_page())
break;
- spin_lock(&hugetlb_lock);
- enqueue_huge_page(page);
- spin_unlock(&hugetlb_lock);
}
max_huge_pages = free_huge_pages = nr_huge_pages = i;
printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
@@ -154,8 +150,8 @@ static void update_and_free_page(struct
page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
1 << PG_private | 1<< PG_writeback);
- set_page_count(&page[i], 0);
}
+ page[1].mapping = NULL;
set_page_count(page, 1);
__free_pages(page, HUGETLB_PAGE_ORDER);
}
@@ -188,12 +184,8 @@ static inline void try_to_free_low(unsig
static unsigned long set_max_huge_pages(unsigned long count)
{
while (count > nr_huge_pages) {
- struct page *page = alloc_fresh_huge_page();
- if (!page)
+ if (!alloc_fresh_huge_page())
return nr_huge_pages;
- spin_lock(&hugetlb_lock);
- enqueue_huge_page(page);
- spin_unlock(&hugetlb_lock);
}
if (count >= nr_huge_pages)
return nr_huge_pages;