Re: [PATCH 1/3] mm/swap.c: pre-sort pages in pagevec for pagevec_lru_move_fn

Alex Shi
2020-12-01T08:21:18Z

在 2020/12/1 下午4:10, Michal Hocko 写道:
> On Tue 01-12-20 16:02:13, Alex Shi wrote:
>> Pages in pagevec may have different lruvec, so we have to do relock in
>> function pagevec_lru_move_fn(), but a relock may cause current cpu wait
>> for long time on the same lock for spinlock fairness reason.
>>
>> Before per memcg lru_lock, we have to bear the relock since the spinlock
>> is the only way to serialize page's memcg/lruvec. Now TestClearPageLRU
>> could be used to isolate pages exculsively, and stable the page's
>> lruvec/memcg. So it gives us a chance to sort the page's lruvec before
>> moving action in pagevec_lru_move_fn. Then we don't suffer from the
>> spinlock's fairness wait.
> Do you have any data to show any improvements from this?
>

Hi Michal,

Thanks for quick response.

Not yet. I am running for data. but according to the lru_add result, there
should be a big gain for multiple memcgs scenario.

Also I don't except a quick accept, just send out the idea for comments
when the thread is still warm. :)

Thanks
Alex