From: Rik van Riel <riel@redhat.com>
To: rmk@arm.linux.org.uk
Cc: linux-mm@kvack.org, Arjan Van de Ven <arjanv@redhat.com>
Subject: [PATCH] speed up fork performance
Date: Fri, 27 Aug 2004 10:09:38 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44.0408271006340.10272-100000@chimarrao.boston.redhat.com> (raw)
OK, this patch is _completely_ untested, but since I'm about to run
off to a conference I guess I should get it to you anyway.
Basically in 2.6 lru_cache_add_active() takes an extra reference to
the page, but do_wp_page() and friends don't expect a private anonymous
page to have 2 references instead of 1. This little patchlet changes
can_share_swap_page() and exclusive_swap_page() to expect the extra
reference.
Note that we cannot test for PageLRU(page) since lru_cache_add_active()
uses a delayed insertion onto the LRU, so the PG_lru might not get set
for a while...
Use at your own risk.
--- linux-2.6.9-rc1/mm/swapfile.c.blah 2004-08-27 09:51:54.000000000 -0400
+++ linux-2.6.9-rc1/mm/swapfile.c 2004-08-27 09:55:38.000000000 -0400
@@ -291,7 +291,8 @@ static int exclusive_swap_page(struct pa
if (p->swap_map[swp_offset(entry)] == 1) {
/* Recheck the page count with the swapcache lock held.. */
spin_lock_irq(&swapper_space.tree_lock);
- if (page_count(page) == 2)
+ /* Process, swapcache and LRU each have a reference. */
+ if (page_count(page) == 3)
retval = 1;
spin_unlock_irq(&swapper_space.tree_lock);
}
@@ -315,15 +316,17 @@ int can_share_swap_page(struct page *pag
if (!PageLocked(page))
BUG();
switch (page_count(page)) {
- case 3:
+ case 4:
if (!PagePrivate(page))
break;
/* Fallthrough */
- case 2:
+ case 3:
if (!PageSwapCache(page))
break;
retval = exclusive_swap_page(page);
break;
+ case 2:
+ /* The LRU takes 1 reference */
case 1:
if (PageReserved(page))
break;
--
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next reply other threads:[~2004-08-27 14:09 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-08-27 14:09 Rik van Riel [this message]
2004-08-27 14:30 ` Russell King
2004-08-27 14:40 ` Mika Penttilä
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