Re: Autotune swappiness01

[Andrew Morton]

Con Kolivas <kernel@xxxxxxxxxxx> wrote:
>
> >> It has the effect 
> >> of being fairly aggressive at avoiding loss of applications to swap under 
> >> conditions of heavy or sustained file stress while allowing applications to 
> >> swap out under what would be considered "application" memory stresses on a 
> >> desktop.
> > 
> > But decreasing /proc/sys/vm/swappiness does that too?
> 
> Low memory boxes and ones that are heavily laden with applications find that 
> ends up making things slow down trying to keep all applications in physical 
> ram.

Doesn't that mean that swappiness was decreased by too much?

> > 
> >> It has no measurable effect on any known benchmarks.
> > 
> > So how are we to evaluate the desirability of the patch???
> 
> Get desktop users to report back their experiences which is what I have 
> currently. Sorry we're in the realm of subjectivity again.

Seriously, we've seen placebo effects before...

> > Shouldn't mapped_bias be local to refill_inactive_zone()?
> 
> That is so a followup patch can use it elsewhere...

erk.  I guess it's OK because the thing is derived from global state which
changes slowly over time.

> > Why is `swappiness' getting squared?  AFAICT this will simply make the
> > swappiness control behave nonlinearly, which seems undesirable?
> 
> To parallel the nonlinear nature of the mapped bias effect. 

That doesn't really answer my question?  What goes wrong if swappiness is
not squared?
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