mpd5/Netgraph issues after upgrading to 7.4

[Przemyslaw Frasunek]

> Use command "vmstat -z|egrep 'ITEM|NetGraph'" and check FAILURES column.
> If you see non-zero values there, you need to increase netgraph memory limits
> net.graph.maxdata and net.graph.maxalloc using /boot/loader.conf.

Thanks, indeed it helped a lot. I also noticed that other zones have
non-zero failure counters:

UMA Slabs:                 64,        0,     2666,     1051,   128676,
    127
128 Bucket:               524,        0,     1455,      316,    82489,
97401821
g_bio:                    132,        0,        0,     3190, 11471737,
      3
ata_request:              192,        0,        0,     1880,  2905852,
    378
rtentry:                  124,        0,     2513,     1765,   802803,
    132
pffrent:                   16,     5075,      175,     3073, 48983719,
      6
pffrag:                    48,        0,       39,     3081, 15699916,
    216

I'm quite anxious about "ata_request" failures.