Hugh Dickins wrote:
Replace pagevecs in putback_lru_pages() and move_active_pages_to_lru()
by lists of pages_to_free: then apply Konstantin Khlebnikov's
free_hot_cold_page_list() to them instead of pagevec_release().
Which simplifies the flow (no need to drop and retake lock whenever
pagevec fills up) and reduces stale addresses in stack backtraces
(which often showed through the pagevecs); but more importantly,
removes another 120 bytes from the deepest stacks in page reclaim.
Although I've not recently seen an actual stack overflow here with
a vanilla kernel, move_active_pages_to_lru() has often featured in
deep backtraces.
However, free_hot_cold_page_list() does not handle compound pages
(nor need it: a Transparent HugePage would have been split by the
time it reaches the call in shrink_page_list()), but it is possible
for putback_lru_pages() or move_active_pages_to_lru() to be left
holding the last reference on a THP, so must exclude the unlikely
compound case before putting on pages_to_free.
Remove pagevec_strip(), its work now done in move_active_pages_to_lru().
The pagevec in scan_mapping_unevictable_pages() remains in mm/vmscan.c,
but that is never on the reclaim path, and cannot be replaced by a list.
Signed-off-by: Hugh Dickins<hughd@xxxxxxxxxx>
Nice patch
Reviewed-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
@@ -1398,12 +1398,10 @@ putback_lru_pages(struct mem_cgroup_zone
struct list_head *page_list)
{
struct page *page;
- struct pagevec pvec;
+ LIST_HEAD(pages_to_free);
struct zone *zone = mz->zone;
As I see, this patch is on top "memcg naturalization" patchset,
it does not apply clearly against Linus tree.
> + if (put_page_testzero(page)) {
> + __ClearPageLRU(page);
> + __ClearPageActive(page);
> + del_page_from_lru_list(zone, page, lru);
> +
> + if (unlikely(PageCompound(page))) {
> + spin_unlock_irq(&zone->lru_lock);
There is good place for VM_BUG_ON(!PageHead(page));
> + (*get_compound_page_dtor(page))(page);
> + spin_lock_irq(&zone->lru_lock);
> + } else
> + list_add(&page->lru,&pages_to_free);
> }
> }
> __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
> __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
>
> spin_unlock_irq(&zone->lru_lock);
> - pagevec_release(&pvec);
> + free_hot_cold_page_list(&pages_to_free, 1);
> }
>
> static noinline_for_stack void
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