Re: [PATCH 5/3] mm, vmscan: make zone_reclaimable_pages more precise

From: David Rientjes
Date: Thu Jan 28 2016 - 18:20:43 EST

On Thu, 28 Jan 2016, Michal Hocko wrote:

> From: Michal Hocko <mhocko@xxxxxxxx>
> zone_reclaimable_pages is used in should_reclaim_retry which uses it to
> calculate the target for the watermark check. This means that precise
> numbers are important for the correct decision. zone_reclaimable_pages
> uses zone_page_state which can contain stale data with per-cpu diffs
> not synced yet (the last vmstat_update might have run 1s in the past).
> Use zone_page_state_snapshot in zone_reclaimable_pages instead. None
> of the current callers is in a hot path where getting the precise value
> (which involves per-cpu iteration) would cause an unreasonable overhead.
> Suggested-by: David Rientjes <rientjes@xxxxxxxxxx>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>

Acked-by: David Rientjes <rientjes@xxxxxxxxxx>