svn commit: r267858 - in head/sys/dev: virtio/balloon xen/balloon

[Alfred Perlstein]

On 6/25/14 6:49 AM, Andriy Gapon wrote:
> On 25/06/2014 17:44, Attilio Rao wrote:
>> Why? If VM needs more wired memory I assume that we can tune up the
>> default value of max_wired?
>>
>> I think that however your case makes an interesting point: if we want
>> to make unmanaged pages as inherently wired, we likely need a little
>> bit higher max_wired value. When I completed a patch for this, pho@
>> couldn't reproduce any similar issue even with stress-testing (and
>> also, the places to allocate unmanaged pages and not requesting
>> VM_ALLOC_WIRED were very little, almost 0, with the exception of
>> vm_page_alloc_contig() calls) but I think it is a valid proposition.
>>
>> However I would still like to have more control on kernel-specific
>> wired memory for processes. I'm for example thinking to ARC vs. buffer
>> cache, where I expect the wired memory consumption to be much bigger
>> for the former case.
> My humble opinion is that userland page wiring should be tuned via
> resource limits and that vm.max_wired could be retired altogether.
> Kernel wiring ignores the knob anyway.
>
I think the goal of the limit as it stands would not to let the total 
amount of wired pages reach a bad point due to a userland program 
pushing it over the limit.

Basically userland wants to know how many pages the kernel has wired in 
order to avoid asking for too many pages and making the system implode.