Re: [PATCH] mm, swap: Make VMA based swap readahead configurable

[Minchan Kim]

On Wed, Sep 27, 2017 at 03:50:34PM +0200, Michal Hocko wrote:
> On Wed 27-09-17 22:41:17, Minchan Kim wrote:
> > On Wed, Sep 27, 2017 at 03:22:41PM +0200, Michal Hocko wrote:
> [...]
> > > simply cannot disable swap readahead when page-cluster is 0?
> > 
> > That's was what I want really but Huang want to use two readahead
> > algorithms in parallel so he wanted to keep two separated disable
> > knobs.
> 
> If it breaks existing and documented behavior then it is a clear
> regression and it should be fixed. I do not see why this should be
> disputable at all.

Indeed but Huang doesn't think so. He has thought it's not a regression.
Frankly speaking, I'm really bored of discussing with it.
https://marc.info/?l=linux-mm&m=150526413319763&w=2

So I passed the decision to Andrew.
http://lkml.kernel.org/r/<20170913014019.GB29422@bbox>

The config option idea is compromise approach although I don't like it
and still believe it's simple clear *regression* so 0 page-cluster
should keep the swap readahead disabled.

> 
> Working around an issue with a config option sounds like the wrong way
> to go because those who cannot do that unconditionally would still see a
> regression.

I absolutely agree but as I said, the discussion was not productive
even though I did best effort to persuade. That's all for my side as
contributor/reviewer. Decision is up to maintainer. ;-)

Thanks for the opinion, Michal.