axe vm.max_wired

[Andriy Gapon]

on 02/02/2013 18:25 Konstantin Belousov said the following:
> On Fri, Feb 01, 2013 at 10:23:46AM +0200, Andriy Gapon wrote:
>> So, I still think that vm.max_wired as it is used now is too arbitrary and too
>> indiscriminate to be useful.
> It is sized well to the default size of the buffer map, which takes 10%
> of the physical RAM of the machine. Since buffers wiring the pages, be
> it VMIO or malloc buffer, this leaves 20% for other things, like mbufs,
> page tables and user wires.

That's the attitude that I don't agree with.
"We leave 20% for user wirings, that should be enough for everyone."
If it's not enough then you must tune.

I rather prefer an approach where we say this is the least amount of memory that
should stay unwired.  The rest is up to a user.

>> There are other tools to limit page wiring by userland e.g. memlocked limit.
> The memlock limit is per-process. It is completely useless as the safety
> measure.

There is also a limit on number of processes, etc.

>> But, as I've said in the original email, I can agree with vm.max_wired
>> usefulness if it is set to something more reasonable by default.
>> IMO, it should not be a fixed percentage of available memory, it should be
>> derived from other VM thresholds related to paging.
> 
> Might be. Please provide a suggestion or better, a change.

On my to do list.

-- 
Andriy Gapon