From: Johannes Weiner <hannes@xxxxxxxxxxx> Subject: mm: workingset: let cache workingset challenge anon We activate cache refaults with reuse distances in pages smaller than the size of the total cache. This allows new pages with competitive access frequencies to establish themselves, as well as challenge and potentially displace pages on the active list that have gone cold. However, that assumes that active cache can only replace other active cache in a competition for the hottest memory. This is not a great default assumption. The page cache might be thrashing while there are enough completely cold and unused anonymous pages sitting around that we'd only have to write to swap once to stop all IO from the cache. Activate cache refaults when their reuse distance in pages is smaller than the total userspace workingset, including anonymous pages. Reclaim can still decide how to balance pressure among the two LRUs depending on the IO situation. Rotational drives will prefer avoiding random IO from swap and go harder after cache. But fundamentally, hot cache should be able to compete with anon pages for a place in RAM. Link: http://lkml.kernel.org/r/20200520232525.798933-6-hannes@xxxxxxxxxxx Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/workingset.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) --- a/mm/workingset.c~mm-workingset-let-cache-workingset-challenge-anon +++ a/mm/workingset.c @@ -277,8 +277,8 @@ void workingset_refault(struct page *pag struct mem_cgroup *eviction_memcg; struct lruvec *eviction_lruvec; unsigned long refault_distance; + unsigned long workingset_size; struct pglist_data *pgdat; - unsigned long active_file; struct mem_cgroup *memcg; unsigned long eviction; struct lruvec *lruvec; @@ -310,7 +310,6 @@ void workingset_refault(struct page *pag goto out; eviction_lruvec = mem_cgroup_lruvec(eviction_memcg, pgdat); refault = atomic_long_read(&eviction_lruvec->inactive_age); - active_file = lruvec_page_state(eviction_lruvec, NR_ACTIVE_FILE); /* * Calculate the refault distance @@ -345,10 +344,18 @@ void workingset_refault(struct page *pag /* * Compare the distance to the existing workingset size. We - * don't act on pages that couldn't stay resident even if all - * the memory was available to the page cache. + * don't activate pages that couldn't stay resident even if + * all the memory was available to the page cache. Whether + * cache can compete with anon or not depends on having swap. */ - if (refault_distance > active_file) + workingset_size = lruvec_page_state(eviction_lruvec, NR_ACTIVE_FILE); + if (mem_cgroup_get_nr_swap_pages(memcg) > 0) { + workingset_size += lruvec_page_state(eviction_lruvec, + NR_INACTIVE_ANON); + workingset_size += lruvec_page_state(eviction_lruvec, + NR_ACTIVE_ANON); + } + if (refault_distance > workingset_size) goto out; SetPageActive(page); _
