Tracking down what has inact pages locked up

Karl Denninger karl at denninger.net
Tue Mar 18 19:36:11 UTC 2014


On 3/18/2014 2:05 PM, John Baldwin wrote:
> On Sunday, March 16, 2014 4:36:06 pm Karl Denninger wrote:
>> Is there a reasonable way to determine who or what has that memory
>> locked up -- and thus why the vm system is not demoting that space into
>> the cache bucket so it can be freed (which, if my understanding is
>> correct, should be happening long before now!)
> I have a hackish thing (for 8.x, might work on 10.x) to let you figure out
> what is using up RAM.  This should perhaps go into the base system at some
> point.
>
> Grab the bits at http://people.freebsd.org/~jhb/vm_objects/
>
> You will want to build the kld first and use 'make load' to load it.  It adds
> a new sysctl that dumps info about all the VM objects in the system.  You can
> then build the 'vm_objects' tool and run it.  It can take a while to run if
> you have NFS mounts, so I typically save its output to a file first and then
> use sort on the results.  sort -n will show you the largest consumer of RAM,
> sort -n -k 3 will show you the largest consumer of inactive pages.  Note
> that 'df' and 'ph' objects are anonymous, and that filename paths aren't
> always reliable, but this can still be useful.
>
Thanks.

I suspect the cause of the huge inact consumption is a RAM leak in the 
NAT code in IPFW.  It was not occurring in 9.2-STABLE, but is on 
10.0-STABLE, and reverting to natd in userland stops it -- which 
pretty-well isolates where it's coming from.

-- 
-- Karl
karl at denninger.net


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