Re: [patch 1/1] vmscan: give referenced, active and unmapped pages a second trip around the LRU

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

akpm@linux-foundation.org wrote:
> From: Andrew Morton <akpm@linux-foundation.org>
> 
> Martin spotted this.
> 
> In the original rmap conversion in 2.5.32 we broke aging of pagecache pages on
> the active list: we deactivate these pages even if they had PG_referenced set.

IIRC this is done to make sure that we reclaim page cache pages
ahead of mapped anonymous pages.

> We should instead clear PG_referenced and give these pages another trip around
> the active list.

A side effect of this is that the page will now need TWO references
to be promoted back to the active list from the inactive list.

The current code leaves PG_referenced set, so that the first access
to a page cache page that was demoted to the inactive list will cause
that page to be moved back to the active list.

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