Fibre channel slow in NetBSD 9.0

[Dima Veselov <kab00m%lich.phys.spbu.ru@localhost>]

Greetings,

One of my servers have root on FC via isp(4). Recently it was
updated to 9-STABLE and the server seem to work slower than it
did on 8-STABLE. This seems not to be about read/write speed (dd
test show big numbers). In certain cases it is "stuck" with IO
writes. Eventually it had big load and I saw the situation -
iostat show small MB/s, but about 20 w/s and at the same time
most of processes in top(1) are in kqueue state, sometimes top
three change to tstile and return back to kqueue. During that
load it is hard to use command-line - it is sticking on any
IO operation, but top do not show significant user or interrupt
load. However, it is not overwhelmed, it feel good after load
get reduced.

I assume lot of processes in same state and incapability
of doing 20-50 writes a second means I have a problem here.

What the direction to work this problem out?

--
Sincerely yours,
Dima Veselov
Physics R&D Establishment of Saint-Petersburg University