On Wed, Mar 27, 2024 at 09:54:01AM +0100, Vlastimil Babka wrote:
> On 3/20/24 7:02 PM, Johannes Weiner wrote:
> > Free page accounting currently happens a bit too high up the call
> > stack, where it has to deal with guard pages, compaction capturing,
> > block stealing and even page isolation. This is subtle and fragile,
> > and makes it difficult to hack on the code.
> >
> > Now that type violations on the freelists have been fixed, push the
> > accounting down to where pages enter and leave the freelist.
>
> Awesome!
>
> > Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
>
> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
>
> Just some nits:
>
> > @@ -1314,10 +1349,10 @@ static inline void expand(struct zone *zone, struct page *page,
> > * Corresponding page table entries will not be touched,
> > * pages will stay not present in virtual address space
> > */
> > - if (set_page_guard(zone, &page[size], high, migratetype))
> > + if (set_page_guard(zone, &page[size], high))
> > continue;
> >
> > - add_to_free_list(&page[size], zone, high, migratetype);
> > + add_to_free_list(&page[size], zone, high, migratetype, false);
>
> This is account_freepages() in the hot loop, what if we instead used
> __add_to_free_list(), sum up nr_pages and called account_freepages() once
> outside of the loop?
Good idea. I'll send a fixlet for that.
> > set_buddy_order(&page[size], high);
> > }
> > }
>
> <snip>
>
> > diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> > index 042937d5abe4..914a71c580d8 100644
> > --- a/mm/page_isolation.c
> > +++ b/mm/page_isolation.c
> > @@ -252,7 +252,8 @@ static void unset_migratetype_isolate(struct page *page, int migratetype)
> > * Isolating this block already succeeded, so this
> > * should not fail on zone boundaries.
> > */
> > - WARN_ON_ONCE(!move_freepages_block_isolate(zone, page, migratetype));
> > + WARN_ON_ONCE(!move_freepages_block_isolate(zone, page,
> > + migratetype));
> > } else {
> > set_pageblock_migratetype(page, migratetype);
> > __putback_isolated_page(page, order, migratetype);
>
> Looks like a drive-by edit of an extra file just to adjust identation.
Argh, yeah, I think an earlier version mucked with the signature and I
didn't undo that cleanly. I'll send a fixlet for that too.
Thanks for the review!
