Re: [PATCH 01/10] mm: allow swappiness that prefers anon over file

[Johannes Weiner]

On Thu, Jun 09, 2016 at 10:01:07AM +0900, Minchan Kim wrote:
> A system has big HDD storage and SSD swap.
> 
> HDD:    200 IOPS
> SSD: 100000 IOPS
> From https://en.wikipedia.org/wiki/IOPS
> 
> So, speed gap is 500x.
> x + 500x = 200
> If we use PCIe-SSD, the gap will be larger.
> That's why I said 200 is enough to represent speed gap.

Ah, I see what you're saying.

Yeah, that's unfortunately a limitation in the current ABI. Extending
the range to previously unavailable settings is doable; changing the
meaning of existing values is not. We'd have to add another interface.

> Such system configuration is already non-sense so it is okay to ignore such
> usecases?

I'm not sure we have to be proactive about it, but we can always add a
more fine-grained knob to override swappiness when somebody wants to
use such a setup in practice.