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hugetlb: decrease hugetlb_lock cycling in gather_surplus_huge_pages

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To reduce hugetlb_lock acquisitions and releases when freeing excess surplus
pages, scan the page list in two parts.  First, transfer the needed pages to
the hugetlb pool.  Then drop the lock and free the remaining pages back to the
buddy allocator.

In the common case there are zero excess pages and no lock operations are
required.

Thanks Mel Gorman for this improvement.

Signed-off-by: Adam Litke <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: William Lee Irwin III <[email protected]>
Cc: Andy Whitcroft <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: David Gibson <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Adam Litke 2008-04-28 02:12:20 -07:00 • committed by Linus Torvalds
commit 19fc3f0acd
1 changed files with 12 additions and 5 deletions
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17
mm/hugetlb.c
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@ -372,11 +372,19 @@ retry:
resv_huge_pages += delta;
ret = 0;
free:
/* Free the needed pages to the hugetlb pool */
list_for_each_entry_safe(page, tmp, &surplus_list, lru) {
if ((--needed) < 0)
break;
list_del(&page->lru);
if ((--needed) >= 0)
enqueue_huge_page(page);
else {
enqueue_huge_page(page);
}
/* Free unnecessary surplus pages to the buddy allocator */
if (!list_empty(&surplus_list)) {
spin_unlock(&hugetlb_lock);
list_for_each_entry_safe(page, tmp, &surplus_list, lru) {
list_del(&page->lru);
/*
* The page has a reference count of zero already, so
* call free_huge_page directly instead of using
@ -384,10 +392,9 @@ free:
* unlocked which is safe because free_huge_page takes
* hugetlb_lock before deciding how to free the page.
*/
spin_unlock(&hugetlb_lock);
free_huge_page(page);
spin_lock(&hugetlb_lock);
}
spin_lock(&hugetlb_lock);
}
return ret;