On Wed, Apr 18, 2012 at 12:23 AM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> (2012/04/18 6:17), Ying Han wrote:
>
>> On Wed, Mar 28, 2012 at 3:51 AM, KAMEZAWA Hiroyuki
>> <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
>>> Consolidate a code for setting pc->mem_cgroup and USED bit which requires smp_wmb().
>>> And remove a macro PCGF_NOCOPY_AT_SPLIT which isn't helpful to read code, now.
>>>
>>> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
>>> ---
>>> include/linux/page_cgroup.h | 18 ++++++++++++++++++
>>> mm/memcontrol.c | 18 ++++--------------
>>> 2 files changed, 22 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h
>>> index 92768cb..2707809 100644
>>> --- a/include/linux/page_cgroup.h
>>> +++ b/include/linux/page_cgroup.h
>>> @@ -1,6 +1,8 @@
>>> #ifndef __LINUX_PAGE_CGROUP_H
>>> #define __LINUX_PAGE_CGROUP_H
>>>
>>> +#include <linux/smp.h>
>>> +
>>> enum {
>>> /* flags for mem_cgroup */
>>> PCG_LOCK, /* Lock for pc->mem_cgroup and following bits. */
>>> @@ -94,6 +96,22 @@ pc_set_mem_cgroup(struct page_cgroup *pc, struct mem_cgroup *memcg)
>>> pc->mem_cgroup = memcg;
>>> }
>>>
>>> +static inline void
>>> +pc_set_mem_cgroup_and_flags(struct page_cgroup *pc, struct mem_cgroup *memcg,
>>> + unsigned long flags)
>>> +{
>>> + pc->mem_cgroup = memcg;
>>> + /*
>>> + * We access a page_cgroup asynchronously without lock_page_cgroup().
>>> + * Especially when a page_cgroup is taken from a page, pc's mem_cgroup
>>> + * is accessed after testing USED bit. To make pc's mem_cgroup visible
>>> + * before USED bit, we need memory barrier here.
>>> + * See mem_cgroup_add_lru_list(), etc.
>>> + */
>>> + smp_wmb();
>>> + pc->flags = flags;
>>> +}
>>> +
>>> #else /* CONFIG_CGROUP_MEM_RES_CTLR */
>>> struct page_cgroup;
>>>
>>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>>> index 8077460..d366b60 100644
>>> --- a/mm/memcontrol.c
>>> +++ b/mm/memcontrol.c
>>> @@ -2511,16 +2511,7 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
>>> }
>>> }
>>>
>>> - pc_set_mem_cgroup(pc, memcg);
>>> - /*
>>> - * We access a page_cgroup asynchronously without lock_page_cgroup().
>>> - * Especially when a page_cgroup is taken from a page, pc's mem_cgroup
>>> - * is accessed after testing USED bit. To make pc's mem_cgroup visible
>>> - * before USED bit, we need memory barrier here.
>>> - * See mem_cgroup_add_lru_list(), etc.
>>> - */
>>> - smp_wmb();
>>> - SetPageCgroupUsed(pc);
>>
>> I might be confused. We removed this SetPageCgroupUsed() but not
>> adding it back elsewhere ?
>>
>> --Ying
>>
>>> + pc_set_mem_cgroup_and_flags(pc, memcg, BIT(PCG_USED) | BIT(PCG_LOCK));
>
>
> Added here. This sets
>
> | memcg pointer | Used | Locked |
Ah. I missed that part.
Thanks
--Ying
>
>
> Thanks,
> -Kame
>
>
>
>
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