mpd5/Netgraph issues after upgrading to 7.4

[Przemyslaw Frasunek]

> IMO, any kind of memory allocation code (malloc, uma, netgraph item
> allocator) never return EPERM, they return ENOMEM or ENOBUFS.
> 
> So, there is a bug somewhere else.

I think so, but for me it still looks like resource shortage.  As I wrote
before, when EPERM starts appearing, I'm unable to run "ngctl list".

I observed that on mpd boxes I have very large number of failed allocations from
zone "128 Bucket". On other boxes with the same release (7.4) and the same
amount of physical memory (2 GB), but without mpd5, this value is almost zero.
Also other zones has non-zero number of failures:

[root at kalina-gw ~]# vmstat -z | grep -v ' 0$'
ITEM                     SIZE     LIMIT      USED      FREE  REQUESTS  FAILURES

UMA Slabs:                 64,        0,     3172,      427,     9555,       21
64 Bucket:                268,        0,      199,       39,      467,       45
128 Bucket:               524,        0,      558,      121,    13258, 64298286
64:                        64,        0,    18525,     1889, 328077543,        8
128:                      128,        0,    16822,     1538,  1718123,       31
mbuf:                     256,        0,        3,     7130, 282690299,       65
udp_inpcb:                180,    25608,      348,      554,  5052711,        3

(above is on mpd box after 8 hours of uptime)

[root at pkp-gw ~]# vmstat -z | grep -v ' 0$'
ITEM                     SIZE     LIMIT      USED      FREE  REQUESTS  FAILURES

64 Bucket:                268,        0,      193,       87,      514,       53
128 Bucket:               524,        0,     7621,        2,  3003617,     1225
pfsrctrpl:                124,    10013,        0,     1426, 14172484,  2979678

(and this is on non-mpd box after 355 days of uptime)

I'm going to try to track down origin of EPERMs by adding some debug printfs in
netgraph code.