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memcg: cleanup mem_cgroup_move_parent() 

mem_cgroup_move_parent() calls try_charge first and cancel_charge on
failure.  IMHO, charge/uncharge(especially charge) is high cost operation,
so we should avoid it as far as possible.

This patch tries to delay try_charge in mem_cgroup_move_parent() by
re-ordering checks it does.

And this patch renames mem_cgroup_move_account() to
__mem_cgroup_move_account(), changes the return value of
__mem_cgroup_move_account() from int to void, and adds a new
wrapper(mem_cgroup_move_account()), which checks whether a @pc is valid
for moving account and calls __mem_cgroup_move_account().

This patch removes the last caller of trylock_page_cgroup(), so removes
its definition too.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Daisuke Nishimura 2009-12-15 16:47:11 -08:00 committed by Linus Torvalds
parent a3032a2c15
commit 57f9fd7d25
2 changed files with 37 additions and 54 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
include/linux/page_cgroup.h
View File

@ -57,6 +57,8 @@ static inline void ClearPageCgroup##uname(struct page_cgroup *pc) \
static inline int TestClearPageCgroup##uname(struct page_cgroup *pc) \
{ return test_and_clear_bit(PCG_##lname, &pc->flags); }
TESTPCGFLAG(Locked, LOCK)
/* Cache flag is set only once (at allocation) */
TESTPCGFLAG(Cache, CACHE)
CLEARPCGFLAG(Cache, CACHE)
@ -86,11 +88,6 @@ static inline void lock_page_cgroup(struct page_cgroup *pc)
bit_spin_lock(PCG_LOCK, &pc->flags);
}
static inline int trylock_page_cgroup(struct page_cgroup *pc)
{
return bit_spin_trylock(PCG_LOCK, &pc->flags);
}
static inline void unlock_page_cgroup(struct page_cgroup *pc)
{
bit_spin_unlock(PCG_LOCK, &pc->flags);

84
mm/memcontrol.c
View File

@ -1613,27 +1613,22 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
}
/**
* mem_cgroup_move_account - move account of the page
* __mem_cgroup_move_account - move account of the page
* @pc: page_cgroup of the page.
* @from: mem_cgroup which the page is moved from.
* @to: mem_cgroup which the page is moved to. @from != @to.
*
* The caller must confirm following.
* - page is not on LRU (isolate_page() is useful.)
*
* returns 0 at success,
* returns -EBUSY when lock is busy or "pc" is unstable.
* - the pc is locked, used, and ->mem_cgroup points to @from.
*
* This function does "uncharge" from old cgroup but doesn't do "charge" to
* new cgroup. It should be done by a caller.
*/
static int mem_cgroup_move_account(struct page_cgroup *pc,
static void __mem_cgroup_move_account(struct page_cgroup *pc,
struct mem_cgroup *from, struct mem_cgroup *to)
{
struct mem_cgroup_per_zone *from_mz, *to_mz;
int nid, zid;
int ret = -EBUSY;
struct page *page;
int cpu;
struct mem_cgroup_stat *stat;
@ -1641,20 +1636,9 @@ static int mem_cgroup_move_account(struct page_cgroup *pc,
VM_BUG_ON(from == to);
VM_BUG_ON(PageLRU(pc->page));
nid = page_cgroup_nid(pc);
zid = page_cgroup_zid(pc);
from_mz = mem_cgroup_zoneinfo(from, nid, zid);
to_mz = mem_cgroup_zoneinfo(to, nid, zid);
if (!trylock_page_cgroup(pc))
return ret;
if (!PageCgroupUsed(pc))
goto out;
if (pc->mem_cgroup != from)
goto out;
VM_BUG_ON(!PageCgroupLocked(pc));
VM_BUG_ON(!PageCgroupUsed(pc));
VM_BUG_ON(pc->mem_cgroup != from);
if (!mem_cgroup_is_root(from))
res_counter_uncharge(&from->res, PAGE_SIZE);
@ -1683,15 +1667,28 @@ static int mem_cgroup_move_account(struct page_cgroup *pc,
css_get(&to->css);
pc->mem_cgroup = to;
mem_cgroup_charge_statistics(to, pc, true);
ret = 0;
out:
unlock_page_cgroup(pc);
/*
* We charges against "to" which may not have any tasks. Then, "to"
* can be under rmdir(). But in current implementation, caller of
* this function is just force_empty() and it's garanteed that
* "to" is never removed. So, we don't check rmdir status here.
*/
}
/*
* check whether the @pc is valid for moving account and call
* __mem_cgroup_move_account()
*/
static int mem_cgroup_move_account(struct page_cgroup *pc,
struct mem_cgroup *from, struct mem_cgroup *to)
{
int ret = -EINVAL;
lock_page_cgroup(pc);
if (PageCgroupUsed(pc) && pc->mem_cgroup == from) {
__mem_cgroup_move_account(pc, from, to);
ret = 0;
}
unlock_page_cgroup(pc);
return ret;
}
@ -1713,38 +1710,27 @@ static int mem_cgroup_move_parent(struct page_cgroup *pc,
if (!pcg)
return -EINVAL;
ret = -EBUSY;
if (!get_page_unless_zero(page))
goto out;
if (isolate_lru_page(page))
goto put;
parent = mem_cgroup_from_cont(pcg);
ret = __mem_cgroup_try_charge(NULL, gfp_mask, &parent, false, page);
if (ret || !parent)
return ret;
if (!get_page_unless_zero(page)) {
ret = -EBUSY;
goto uncharge;
}
ret = isolate_lru_page(page);
if (ret)
goto cancel;
goto put_back;
ret = mem_cgroup_move_account(pc, child, parent);
if (!ret)
css_put(&parent->css); /* drop extra refcnt by try_charge() */
else
mem_cgroup_cancel_charge(parent); /* does css_put */
put_back:
putback_lru_page(page);
if (!ret) {
put_page(page);
/* drop extra refcnt by try_charge() */
css_put(&parent->css);
return 0;
}
cancel:
put:
put_page(page);
uncharge:
mem_cgroup_cancel_charge(parent);
out:
return ret;
}