Re: [PATCH] vmscan: zone_reclaim don't call disable_swap_token()

From: KOSAKI Motohiro
Date: Sun Jun 27 2010 - 21:37:56 EST

> On Fri, Jun 25, 2010 at 5:31 PM, KOSAKI Motohiro
> <kosaki.motohiro@xxxxxxxxxxxxxx> wrote:
> > Swap token don't works when zone reclaim is enabled since it was born.
> > Because __zone_reclaim() always call disable_swap_token()
> > unconditionally.
> >
> > This kill swap token feature completely. As far as I know, nobody want
> > to that. Remove it.
> >
> In f7b7fd8f3ebbb, Rik added disable_swap_token.
> At that time, sc.priority in zone_reclaim is zero so it does make sense.
> But in a92f71263a, Christoph changed the priority to begin from
> ZONE_RECLAIM_PRIORITY with remained disable_swap_token. It doesn't
> make sense.
> So doesn't we add disable_swap_token following as than removing?

f7b7fd8f3ebbb says disable_swap_token was introduced to prevent OOM.
but zone reclaim failure don't make OOM. instead, fallback to try_to_free_pages().

If the system have really heavy pressure, do_try_to_free_pages()
will call disable_swap_token().

So, What benefit is there?

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