在 2020/1/10 下午4:39, Konstantin Khlebnikov 写道:

On 25/12/2019 12.04, Alex Shi wrote:

quoted

We don't have to add a freeable page into lru and then remove from it.
This change saves a couple of actions and makes the moving more clear.

The SetPageLRU needs to be kept here for list intergrity. Otherwise:

     #0 mave_pages_to_lru                #1 release_pages
                                         if (put_page_testzero())
     if (put_page_testzero())
                                        !PageLRU //skip lru_lock
                                                 list_add(&page->lru,);
     else
         list_add(&page->lru,) //corrupt

Signed-off-by: Alex Shi <redacted>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: yun.wang@linux.alibaba.com
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
  mm/vmscan.c | 16 +++++++---------
  1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 572fb17c6273..8719361b47a0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c

@@ -1852,26 +1852,18 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,

Here is another cleanup: pass only pgdat as argument.

This function reavaluates lruvec for each page under lru lock.
Probably this is redundant for now but could be used in the future (or your patchset already use that).

Thanks a lot for comments, Konstantin!

yes, we could use pgdat here, but since to remove the pgdat later, maybe better to save this change? :)

quoted

      while (!list_empty(list)) {
          page = lru_to_page(list);
          VM_BUG_ON_PAGE(PageLRU(page), page);
+        list_del(&page->lru);
          if (unlikely(!page_evictable(page))) {
-            list_del(&page->lru);
              spin_unlock_irq(&pgdat->lru_lock);
              putback_lru_page(page);
              spin_lock_irq(&pgdat->lru_lock);
              continue;
          }
-        lruvec = mem_cgroup_page_lruvec(page, pgdat);
-

Please leave a comment that we must set PageLRU before dropping our page reference.

Right, I will try to give a comments here.
 

quoted

          SetPageLRU(page);
-        lru = page_lru(page);
-
-        nr_pages = hpage_nr_pages(page);
-        update_lru_size(lruvec, lru, page_zonenum(page), nr_pages);
-        list_move(&page->lru, &lruvec->lists[lru]);
            if (put_page_testzero(page)) {
              __ClearPageLRU(page);
              __ClearPageActive(page);
-            del_page_from_lru_list(page, lruvec, lru);
                if (unlikely(PageCompound(page))) {
                  spin_unlock_irq(&pgdat->lru_lock);

@@ -1880,6 +1872,12 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,

              } else
                  list_add(&page->lru, &pages_to_free);
          } else {
+            lruvec = mem_cgroup_page_lruvec(page, pgdat);
+            lru = page_lru(page);
+            nr_pages = hpage_nr_pages(page);
+
+            update_lru_size(lruvec, lru, page_zonenum(page), nr_pages);
+            list_add(&page->lru, &lruvec->lists[lru]);
              nr_moved += nr_pages;
          }

IMHO It looks better to in this way:> 
SetPageLRU()

if (unlikely(put_page_testzero())) {
 <free>
 continue;
}

<add>

Yes, this looks better!

Thanks
Alex

quoted

      }