On Mon 23-01-17 13:16:37, Johannes Weiner wrote:
> We have an elaborate dirty/writeback throttling mechanism inside the
> reclaim scanner, but for that to work the pages have to go through
> shrink_page_list() and get counted for what they are. Otherwise, we
> mess up the LRU order and don't match reclaim speed to writeback.
>
> Especially during deactivation, there is never a reason to skip dirty
> pages; nothing is even trying to write them out from there. Don't mess
> up the LRU order for nothing, shuffle these pages along.
absolutely agreed.
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> include/linux/mmzone.h | 2 --
> mm/vmscan.c | 14 ++------------
> 2 files changed, 2 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index df992831fde7..338a786a993f 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -236,8 +236,6 @@ struct lruvec {
> #define LRU_ALL_ANON (BIT(LRU_INACTIVE_ANON) | BIT(LRU_ACTIVE_ANON))
> #define LRU_ALL ((1 << NR_LRU_LISTS) - 1)
>
> -/* Isolate clean file */
> -#define ISOLATE_CLEAN ((__force isolate_mode_t)0x1)
> /* Isolate unmapped file */
> #define ISOLATE_UNMAPPED ((__force isolate_mode_t)0x2)
> /* Isolate for asynchronous migration */
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 7bb23ff229b6..0d05f7f3b532 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -87,6 +87,7 @@ struct scan_control {
> /* The highest zone to isolate pages for reclaim from */
> enum zone_type reclaim_idx;
>
> + /* Writepage batching in laptop mode; RECLAIM_WRITE */
> unsigned int may_writepage:1;
>
> /* Can mapped pages be reclaimed? */
> @@ -1373,13 +1374,10 @@ int __isolate_lru_page(struct page *page, isolate_mode_t mode)
> * wants to isolate pages it will be able to operate on without
> * blocking - clean pages for the most part.
> *
> - * ISOLATE_CLEAN means that only clean pages should be isolated. This
> - * is used by reclaim when it is cannot write to backing storage
> - *
> * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
> * that it is possible to migrate without blocking
> */
> - if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) {
> + if (mode & ISOLATE_ASYNC_MIGRATE) {
> /* All the caller can do on PageWriteback is block */
> if (PageWriteback(page))
> return ret;
> @@ -1387,10 +1385,6 @@ int __isolate_lru_page(struct page *page, isolate_mode_t mode)
> if (PageDirty(page)) {
> struct address_space *mapping;
>
> - /* ISOLATE_CLEAN means only clean pages */
> - if (mode & ISOLATE_CLEAN)
> - return ret;
> -
> /*
> * Only pages without mappings or that have a
> * ->migratepage callback are possible to migrate
> @@ -1731,8 +1725,6 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
>
> if (!sc->may_unmap)
> isolate_mode |= ISOLATE_UNMAPPED;
> - if (!sc->may_writepage)
> - isolate_mode |= ISOLATE_CLEAN;
>
> spin_lock_irq(&pgdat->lru_lock);
>
> @@ -1929,8 +1921,6 @@ static void shrink_active_list(unsigned long nr_to_scan,
>
> if (!sc->may_unmap)
> isolate_mode |= ISOLATE_UNMAPPED;
> - if (!sc->may_writepage)
> - isolate_mode |= ISOLATE_CLEAN;
>
> spin_lock_irq(&pgdat->lru_lock);
>
> --
> 2.11.0
>
> --
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--
Michal Hocko
SUSE Labs
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