On 08/29/2017 02:36 AM, Joonsoo Kim wrote:

On Mon, Aug 28, 2017 at 08:45:07AM +0200, Vlastimil Babka wrote:

quoted

+CC linux-api

On 08/28/2017 02:28 AM, Joonsoo Kim wrote:

quoted

On Fri, Aug 25, 2017 at 09:56:10AM +0200, Vlastimil Babka wrote:

Seems reasonable. However, if there is a user who checks
sysctl_lowmem_reserve_ratio entry for HIGHMEM and change it, suggested
interface will cause a problem since it doesn't expose ratio for
HIGHMEM. Am I missing something?

As you explained, it makes little sense to change it for HIGHMEM which
only affects MOVABLE allocations. Also I doubt there are many systems
with both HIGHMEM (implies 32bit) *and* MOVABLE (implies NUMA, memory
hotplug...) zones. So I would just remove it, and if somebody will
really miss it, we can always add it back. In any case, please CC
linux-api on the next version.

If we will accept a change that potentially breaks the user, I think
that making zero as a special value for sysctl_lowmem_reserve_ratio
is better solution. How about this way?

I'd prefer removal, but won't object to zero. Certainly much better than
UINT_MAX.

Thanks.
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