On 2024/1/27 02:01, Nhat Pham wrote:
> On Fri, Jan 26, 2024 at 12:31 AM <chengming.zhou@xxxxxxxxx> wrote:
>>
>> From: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
>>
>> LRU_SKIP can only be returned if we don't ever dropped lru lock, or
>> we need to return LRU_RETRY to restart from the head of lru list.
>
> Ooops. You're right! I just double checked and only LRU_REMOVED_RETRY
> and LRU_RETRY indicate we might have dropped the lock. My bad.
>
>>
>> Actually we may need to introduce another LRU_STOP to really terminate
>> the ongoing shrinking scan process, when we encounter a warm page
>
> Yup. This is what I was trying (and failing) to do. To be honest, this
> needs to be even stronger: short-circuit ALL concurrent/ongoing zswap
> shrinker scan processes that are touching this memcg (as they will
> also shrink into warmer regions going forward). But that's a bit more
> engineering to do. LRU_STOP, which stops this scan process, would be a
> good place to start.
Good suggestion, will look into that more later.
>
>> already in the swap cache. The current list_lru implementation
>> doesn't have this function to early break from __list_lru_walk_one.
>>
>> Fixes: b5ba474f3f51 ("zswap: shrink zswap pool based on memory pressure")
>> Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
>
> Reviewed-by: Nhat Pham <nphamcs@xxxxxxxxx>
Thanks.
>
>> ---
>> mm/zswap.c | 4 +---
>> 1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/mm/zswap.c b/mm/zswap.c
>> index 00e90b9b5417..81cb3790e0dd 100644
>> --- a/mm/zswap.c
>> +++ b/mm/zswap.c
>> @@ -901,10 +901,8 @@ static enum lru_status shrink_memcg_cb(struct list_head *item, struct list_lru_o
>> * into the warmer region. We should terminate shrinking (if we're in the dynamic
>> * shrinker context).
>> */
>> - if (writeback_result == -EEXIST && encountered_page_in_swapcache) {
>> - ret = LRU_SKIP;
>> + if (writeback_result == -EEXIST && encountered_page_in_swapcache)
>> *encountered_page_in_swapcache = true;
>> - }
>>
>> goto put_unlock;
>> }
>> --
>> 2.40.1
>>
