xfs
[Top] [All Lists]

Re: [PATCH 4/5] mm: vmscan: Immediately reclaim end-of-LRU dirty pages w

To: Mel Gorman <mgorman@xxxxxxx>
Subject: Re: [PATCH 4/5] mm: vmscan: Immediately reclaim end-of-LRU dirty pages when writeback completes
From: Johannes Weiner <jweiner@xxxxxxxxxx>
Date: Wed, 13 Jul 2011 18:40:40 +0200
Cc: Linux-MM <linux-mm@xxxxxxxxx>, LKML <linux-kernel@xxxxxxxxxxxxxxx>, XFS <xfs@xxxxxxxxxxx>, Dave Chinner <david@xxxxxxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, Wu Fengguang <fengguang.wu@xxxxxxxxx>, Jan Kara <jack@xxxxxxx>, Rik van Riel <riel@xxxxxxxxxx>, Minchan Kim <minchan.kim@xxxxxxxxx>
In-reply-to: <1310567487-15367-5-git-send-email-mgorman@xxxxxxx>
References: <1310567487-15367-1-git-send-email-mgorman@xxxxxxx> <1310567487-15367-5-git-send-email-mgorman@xxxxxxx>
On Wed, Jul 13, 2011 at 03:31:26PM +0100, Mel Gorman wrote:
> When direct reclaim encounters a dirty page, it gets recycled around
> the LRU for another cycle. This patch marks the page PageReclaim using
> deactivate_page() so that the page gets reclaimed almost immediately
> after the page gets cleaned. This is to avoid reclaiming clean pages
> that are younger than a dirty page encountered at the end of the LRU
> that might have been something like a use-once page.
> 
> Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
> ---
>  include/linux/mmzone.h |    2 +-
>  mm/vmscan.c            |   10 ++++++++--
>  mm/vmstat.c            |    2 +-
>  3 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index c4508a2..bea7858 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -100,7 +100,7 @@ enum zone_stat_item {
>       NR_UNSTABLE_NFS,        /* NFS unstable pages */
>       NR_BOUNCE,
>       NR_VMSCAN_WRITE,
> -     NR_VMSCAN_WRITE_SKIP,
> +     NR_VMSCAN_INVALIDATE,
>       NR_VMSCAN_THROTTLED,
>       NR_WRITEBACK_TEMP,      /* Writeback using temporary buffers */
>       NR_ISOLATED_ANON,       /* Temporary isolated pages from anon lru */
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 9826086..8e00aee 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -834,8 +834,13 @@ static unsigned long shrink_page_list(struct list_head 
> *page_list,
>                        */
>                       if (page_is_file_cache(page) &&
>                                       (!current_is_kswapd() || priority >= 
> DEF_PRIORITY - 2)) {
> -                             inc_zone_page_state(page, NR_VMSCAN_WRITE_SKIP);
> -                             goto keep_locked;
> +                             inc_zone_page_state(page, NR_VMSCAN_INVALIDATE);
> +
> +                             /* Immediately reclaim when written back */
> +                             unlock_page(page);
> +                             deactivate_page(page);
> +
> +                             goto keep_dirty;
>                       }
>  
>                       if (references == PAGEREF_RECLAIM_CLEAN)
> @@ -956,6 +961,7 @@ keep:
>               reset_reclaim_mode(sc);
>  keep_lumpy:
>               list_add(&page->lru, &ret_pages);
> +keep_dirty:
>               VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
>       }

I really like the idea behind this patch, but I think all those pages
are lost as PageLRU is cleared on isolation and lru_deactivate_fn
bails on them in turn.

If I'm not mistaken, the reference from the isolation is also leaked.

<Prev in Thread] Current Thread [Next in Thread>