Re: [PATCH v2] mm/zswap: Check all pool pages instead of one pool pages

Bob Liu
2014-01-21T03:58:55Z

On Tue, Jan 21, 2014 at 11:07 AM, Cai Liu <liucai.lfn@gmail.com> wrote:
> Thanks for your review.
>
> 2014/1/21 Minchan Kim <minchan@kernel.org>:
>> Hello Cai,
>>
>> On Mon, Jan 20, 2014 at 03:50:18PM +0800, Cai Liu wrote:
>>> zswap can support multiple swapfiles. So we need to check
>>> all zbud pool pages in zswap.
>>>
>>> Version 2:
>>> * add *total_zbud_pages* in zbud to record all the pages in pools
>>> * move the updating of pool pages statistics to
>>> alloc_zbud_page/free_zbud_page to hide the details
>>>
>>> Signed-off-by: Cai Liu <cai.liu@samsung.com>
>>> ---
>>> include/linux/zbud.h | 2 +-
>>> mm/zbud.c | 44 ++++++++++++++++++++++++++++++++------------
>>> mm/zswap.c | 4 ++--
>>> 3 files changed, 35 insertions(+), 15 deletions(-)
>>>
>>> diff --git a/include/linux/zbud.h b/include/linux/zbud.h
>>> index 2571a5c..1dbc13e 100644
>>> --- a/include/linux/zbud.h
>>> +++ b/include/linux/zbud.h
>>> @@ -17,6 +17,6 @@ void zbud_free(struct zbud_pool *pool, unsigned long handle);
>>> int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries);
>>> void *zbud_map(struct zbud_pool *pool, unsigned long handle);
>>> void zbud_unmap(struct zbud_pool *pool, unsigned long handle);
>>> -u64 zbud_get_pool_size(struct zbud_pool *pool);
>>> +u64 zbud_get_pool_size(void);
>>>
>>> #endif /* _ZBUD_H_ */
>>> diff --git a/mm/zbud.c b/mm/zbud.c
>>> index 9451361..711aaf4 100644
>>> --- a/mm/zbud.c
>>> +++ b/mm/zbud.c
>>> @@ -52,6 +52,13 @@
>>> #include <linux/spinlock.h>
>>> #include <linux/zbud.h>
>>>
>>> +/*********************************
>>> +* statistics
>>> +**********************************/
>>> +
>>> +/* zbud pages in all pools */
>>> +static u64 total_zbud_pages;
>>> +
>>> /*****************
>>> * Structures
>>> *****************/
>>> @@ -142,10 +149,28 @@ static struct zbud_header *init_zbud_page(struct page *page)
>>> return zhdr;
>>> }
>>>
>>> +static struct page *alloc_zbud_page(struct zbud_pool *pool, gfp_t gfp)
>>> +{
>>> + struct page *page;
>>> +
>>> + page = alloc_page(gfp);
>>> +
>>> + if (page) {
>>> + pool->pages_nr++;
>>> + total_zbud_pages++;
>>
>> Who protect race?
>
> Yes, here the pool->pages_nr and also the total_zbud_pages are not protected.
> I will re-do it.
>
> I will change *total_zbud_pages* to atomic type.

And how about just add total_zbud_pages++ and leave pool->pages_nr in
its original place which already protected by pool->lock?

> For *pool->pages_nr*, one way is to use pool->lock to protect. But I
> think it is too heavy.
> So does it ok to change pages_nr to atomic type too?
>

--
Regards,
--Bob