Re: [PATCH 03/27] xfs: use write_cache_pages for writeback clustering

[Rik van Riel <riel@redhat.com>]

On 07/11/2011 01:20 PM, Johannes Weiner wrote:

> I CC'd Rik for reclaim-wizardry.  But if I am not completly off with
> this there is a chance that the change that let the active list grow
> unscanned may actually have contributed to this single-page writing
> problem becoming worse?

Yes, the patch probably contributed.

However, the patch does help protect the working set in
the page cache from streaming IO, so on balance I believe
we need to keep this change.

What it changes is that the size of the inactive file list
can no longer grow unbounded, keeping it a little smaller
than it could have grown in the past.

> commit 56e49d218890f49b0057710a4b6fef31f5ffbfec
> Author: Rik van Riel<riel@redhat.com>
> Date:   Tue Jun 16 15:32:28 2009 -0700
>
>      vmscan: evict use-once pages first
>
>      When the file LRU lists are dominated by streaming IO pages, evict those
>      pages first, before considering evicting other pages.
>
>      This should be safe from deadlocks or performance problems
>      because only three things can happen to an inactive file page:
>
>      1) referenced twice and promoted to the active list
>      2) evicted by the pageout code
>      3) under IO, after which it will get evicted or promoted
>
>      The pages freed in this way can either be reused for streaming IO, or
>      allocated for something else.  If the pages are used for streaming IO,
>      this pageout pattern continues.  Otherwise, we will fall back to the
>      normal pageout pattern.
>
>      Signed-off-by: Rik van Riel<riel@redhat.com>
>      Reported-by: Elladan<elladan@eskimo.com>
>      Cc: KOSAKI Motohiro<kosaki.motohiro@jp.fujitsu.com>
>      Cc: Peter Zijlstra<peterz@infradead.org>
>      Cc: Lee Schermerhorn<lee.schermerhorn@hp.com>
>      Acked-by: Johannes Weiner<hannes@cmpxchg.org>
>      Signed-off-by: Andrew Morton<akpm@linux-foundation.org>
>      Signed-off-by: Linus Torvalds<torvalds@linux-foundation.org>


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