Re: [PATCH v14 15/20] mm/swap: serialize memcg changes during pagevec_lru_move_fn

Matthew Wilcox
2020-07-04T13:33:55Z

On Sat, Jul 04, 2020 at 09:12:46PM +0800, Alex Shi wrote:
> 在 2020/7/4 下午7:39, Matthew Wilcox 写道:
> > On Sat, Jul 04, 2020 at 07:34:59PM +0800, Alex Shi wrote:
> >> That's a great idea! Guess what the new struct we need would be like this?
> >> I like to try this. :)
> >>
> >>
> >> diff --git a/include/linux/pagevec.h b/include/linux/pagevec.h
> >> index 081d934eda64..d62778c8c184 100644
> >> --- a/include/linux/pagevec.h
> >> +++ b/include/linux/pagevec.h
> >> @@ -20,7 +20,7 @@
> >> struct pagevec {
> >> unsigned char nr;
> >> bool percpu_pvec_drained;
> >> - struct page *pages[PAGEVEC_SIZE];
> >> + struct list_head veclist;
> >> };
> >
> > pagevecs are used not just for LRU. If you want to use a list_head for
> > LRU then define a new structure.
>
> yes, there are much page don't use page->lru, like slab etc. we need a new struct.

That's not what I mean. Slab pages aren't on the LRU anyway.

Consider the callers of page_cache_delete_batch(). These use a pagevec
for a non-LRU purpose, and they will be much slower with a list_head than
with an array.