Re: [PATCH 3/3] vmscan: implement swap token priority decay

[Rik van Riel]

On 05/13/2011 07:42 AM, KOSAKI Motohiro wrote:
> While testing for memcg aware swap token, I observed a swap token
> was often grabbed an intermittent running process (eg init, auditd)
> and they never release a token.
>
> Why? Currently, swap toke priority is only decreased at page fault
> path. Then, if the process sleep immediately after to grab swap
> token, their swap token priority never be decreased. That makes
> obviously undesired result.
>
> This patch implement very poor (and lightweight) priority decay
> mechanism. It only be affect to the above corner case and doesn't
> change swap tendency workload performance (eg multi process qsbench
> load)

Ohhh, good catch.  The original swap token algorithm did
not have this problem, and I never caught the fact that
the replacement (which is better in many ways) does...

> Signed-off-by: KOSAKI Motohiro<kosaki.motohiro@xxxxxxxxxxxxxx>

Reviewed-by: Rik van Riel<riel@xxxxxxxxxx>

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