[PATCH 2/9] mm: avoid calling get_page_unless_zero() when charging cgroups
From: Michel Lespinasse <hidden>
Date: 2011-08-19 07:49:51
Also in:
lkml
Subsystem:
control group - memory resource controller (memcg), memory management, the rest · Maintainers:
Johannes Weiner, Michal Hocko, Roman Gushchin, Shakeel Butt, Andrew Morton, Linus Torvalds
In mem_cgroup_move_parent(), we can avoid the get_page_unless_zero() call by taking a page reference under protection of the zone LRU lock in mem_cgroup_force_empty_list(). In mc_handle_present_pte(), the page count is already known to be nonzero as there is a PTE pointing to it and the page table lock is held. Signed-off-by: Michel Lespinasse <redacted> --- mm/memcontrol.c | 20 ++++++++++---------- 1 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e013b8e..f9439ef 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c@@ -2649,7 +2649,7 @@ out: } /* - * move charges to its parent. + * move charges to its parent. Caller must hold a reference on page. */ static int mem_cgroup_move_parent(struct page *page,
@@ -2669,10 +2669,8 @@ static int mem_cgroup_move_parent(struct page *page, return -EINVAL; ret = -EBUSY; - if (!get_page_unless_zero(page)) - goto out; if (isolate_lru_page(page)) - goto put; + goto out; nr_pages = hpage_nr_pages(page);
@@ -2692,8 +2690,6 @@ static int mem_cgroup_move_parent(struct page *page, compound_unlock_irqrestore(page, flags); put_back: putback_lru_page(page); -put: - put_page(page); out: return ret; }
@@ -3732,11 +3728,12 @@ static int mem_cgroup_force_empty_list(struct mem_cgroup *mem, spin_unlock_irqrestore(&zone->lru_lock, flags); continue; } - spin_unlock_irqrestore(&zone->lru_lock, flags); - page = lookup_cgroup_page(pc); + get_page(page); + spin_unlock_irqrestore(&zone->lru_lock, flags); ret = mem_cgroup_move_parent(page, pc, mem, GFP_KERNEL); + put_page(page); if (ret == -ENOMEM) break;
@@ -5133,9 +5130,12 @@ static struct page *mc_handle_present_pte(struct vm_area_struct *vma, } else if (!move_file()) /* we ignore mapcount for file pages */ return NULL; - if (!get_page_unless_zero(page)) - return NULL; + /* + * The page reference count is guaranteed to be nonzero since + * ptent points to that page and the page table lock is held. + */ + get_page(page); return page; }
--
1.7.3.1
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>