On 12/07/2024 09:50, Zhijian Li (Fujitsu) wrote:
> CPU0 CPU1
> ----------- ---------
> // erase pcp_list
> zone_pcp_disable // pcp->count = 0
>
> lru_cache_diable() __rmqueue_pcplist() // re-add pages to pcp_lsit
> __rmqueue_pcplist() // drop pages from pcp_list
> decay_pcp_high() // drop pages from pcp_list
> loop { ...
> __rmqueue_pcplist() // drop pages from pcp_list,
> // it will be only called a few times during the loop
> scan_movable_pages() ...
> migration_pages() decay_pcp_high() // drop pages from pcp_list, it will be called by
> // a worker periodically during the loop
>
> // wait pcp_list to be empty
> } while (test_pages_isolated())
>
>
> And we noticed that re-add pages to pcp_list in '__rmqueue_pcplist()` only happen once,
> pcp->count changed to 200 from 0 for example.
>
> The later calls to __rmqueue_pcplist() will drop pcp->count by step 1 for each call,
> For example, pcp->count: 199->198->197->196...,
> However it stops calling __rmqueue_pcplist after a few times before pcp->count is dropped to 0.
>
> In the normal/good case, we also noticed that __rmqueue_pcplist() dropped pcp->count to 0.
I doubt all these(after calling zone_pcp_disable())
1. __rmqueue_pcplist() should re-add pages to pcp_list
2. __rmqueue_pcplist() should drop pcp->count till 0 if 1 is true
3. decay_pcp_high() should drop pcp->count till 0, its name and comments don't indicate this.
