em0 with latest driver hangs again and again (without "Watchdog timeout" message!)

[Lev Serebryakov]

Hello, Freebsd-net.

  It's me again, as problem is not solved and no "clear" answer was
received.

  em0 NIC on my storage server hangs every several (2-3) days.
Symptoms are simple: no packets can be send, mbufs are overfilled, "No
buf space to send" error for any program.

    Configuration now is VERY BASIC: no polling, no sysctls or
loader.conf tunables AT ALL. No jumbo frames.

  nic doesn't show any "Watchdog timeout" / "resetting" messages.

  Driver from "em driver, 82574L chip, and possibly ASPM" thread
 doesn't help, really: it seems, that it decrease frequincy of hangs,
 but doesn't eliminate them, but I can not say for sure, may be
 frequency change is only illusion, as it random process.

 I've added diagnostic patch from Michael Tuxen.

 System is cvsupped and built  Mon Feb 21, it is FreeBSD 8-STABLE
(RELENG_8).

  Hardware is:

em0 at pci0:0:25:0:        class=0x020000 card=0x82681043 chip=0x10bd8086 rev=0x02 hdr=0x00
    vendor     = 'Intel Corporation'
    device     = 'Intel 82566DM Gigabit Ethernet Adapter (82566DM)'
    class      = network
    subclass   = ethernet
    bar   [10] = type Memory, range 32, base 0xfeb40000, size 131072, enabled
    bar   [14] = type Memory, range 32, base 0xfeb7a000, size 4096, enabled
    bar   [18] = type I/O Port, range 32, base 0xe880, size 32, enabled
    cap 01[c8] = powerspec 2  supports D0 D3  current D0
    cap 05[d0] = MSI supports 1 message, 64 bit
    cap 09[e0] = vendor (length 6) Intel cap 2 version 0


  Output of ifconfig, vmstat -m, netstat -m, top -Snd 1, sysctl
dev.em.0 is attached.

  Interesting part of diagnostic sysctls:

dev.em.0.queue0.rxd_head: 896
dev.em.0.queue0.rxd_tail: 895
dev.em.0.queue0.rx_irq: 0
dev.em.0.queue0.rx_nxt_refresh: 896
dev.em.0.queue0.rx_nxt_check: 896

-- 
// Black Lion AKA Lev Serebryakov <lev at serebryakov.spb.ru>
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