On Fri, 16 Feb 2018, Dave Hansen wrote:

On 02/16/2018 08:01 AM, Christoph Lameter wrote:

quoted

In order to make this work just right one needs to be able to
know the workload well enough to reserve the right amount
of pages. This is comparable to other reservation schemes.

Yes, but it's a reservation scheme that doesn't show up in MemFree, for
instance.  Even hugetlbfs-reserved memory subtracts from that.

Ok. There is the question if we can get all these reservation schemes
under one hood instead of having page order specific ones in subsystems
like hugetlb.

This has the potential to be really confusing to apps.  If this memory
is now not available to normal apps, they might plow into the invisible
memory limits and get into nasty reclaim scenarios.

Shouldn't this subtract the memory for MemFree and friends?

Ok certainly we could do that. But on the other hand the memory is
available if those subsystems ask for the right order. Its not clear to me
what the right way of handling this is. Right now it adds the reserved
pages to the watermarks. But then under some circumstances the memory is
available. What is the best solution here?

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