Date: Mon, 26 Sep 2005 11:08:53 -0400 From: Benjamin Rosenblum <ben@benswebs.com> To: net@freebsd.org Subject: Re: em(4) receive part wedging randomly at moderate load Message-ID: <43380F05.3070005@benswebs.com> In-Reply-To: <20050926142907.GI91328@cell.sick.ru> References: <20050926142907.GI91328@cell.sick.ru>
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the em driver in itself is extremly buggy. many people, myself
included, are hitting some major problems with this driver that are
causeing some serious issues. i cant transfer any large files to my
server because the em driver panics and drops the connection for 15-20
seconds. its a real pain in the butt when this happens too cause this
is my primary network storage server. i have had to resort to the
backup systems lately because of this problem. i think the entire em
network driver needs to get reworked and all these bugs really need to
be taken care of since this is one of the top like 3 network cards used
in the field today for gig transfer.
Gleb Smirnoff wrote:
> Colleagues,
>
> during last month we are experiencing a nasty problem with em(4)
>driver. Several times a day the receive path of the driver wedges
>for a minute or two. During wedge the transmit part works with
>no problems. The latter fact makes this problem very nasty, because
>the problematic router can't be backed up with help of CARP.
>
>Some details: during the wedge all incoming packets are lost and
>counted as "Missed packets". I've checked this using
>`sysctl dev.em.0.stats=1`. The `dmesg` output is the following:
>
>em0: Excessive collisions = 0
>em0: Symbol errors = 0
>em0: Sequence errors = 0
>em0: Defer count = 0
>em0: Missed Packets = 1266
>em0: Receive No Buffers = 220
>em0: Receive length errors = 0
>em0: Receive errors = 0
>em0: Crc errors = 0
>em0: Alignment errors = 0
>em0: Carrier extension errors = 0
>em0: XON Rcvd = 0
>em0: XON Xmtd = 0
>em0: XOFF Rcvd = 0
>em0: XOFF Xmtd = 0
>em0: Good Packets Rcvd = 28347789
>em0: Good Packets Xmtd = 30911959
>
>There is a clear evidence that command `sysctl dev.em.0.stats=1` itself
>can trigger the wedge. It is important, that the stats are printed
>to a 9600 baud serial console, and this takes about a second. I have
>suspicion, that the wedge happens when kernel doesn't service NIC
>interrupts for some period of time. Yes, some packets should be lost in
>this case, but the wedge must not continue for minutes!
>
>The box is serving 8 - 15 kpps, 70 - 100 MBps. It runs stateful pf(4)
>firewall, with 50k - 80k states. The IP fastforwarding is enabled. The
>average state insert/removal ratio is 300 states per second, however
>sometimes several thousands of states can be removed in one pass. The
>state removal locks the network code for quite a long time, so I guess
>that wedge happens exactly when a lot of states are removed. The NIC
>interrupts aren't serviced for some time and it wedges.
>
>The hardware is Supermicro server, with two onboard NICs:
>
>dev.em.0.%pnpinfo: vendor=0x8086 device=0x1075 subvendor=0x8086 subdevice=0x1075 class=0x020000
>dev.em.1.%pnpinfo: vendor=0x8086 device=0x1076 subvendor=0x8086 subdevice=0x1076 class=0x020000
>
>The NIC is plugged in Cisco Catalyst 6509 gigabit ethernet port. No
>errors are counted on switch port.
>
>To workaround the problem, I have made the following patch:
>
>@@ -1650,12 +1651,18 @@
> struct ifnet *ifp;
> struct adapter * adapter = arg;
> ifp = adapter->ifp;
>+ uint64_t ompc;
>
> EM_LOCK(adapter);
>
> em_check_for_link(&adapter->hw);
> em_print_link_status(adapter);
>- em_update_stats_counters(adapter);
>+ ompc = adapter->stats.mpc;
>+ em_update_stats_counters(adapter);
>+ if (adapter->stats.mpc > ompc) {
>+ printf("em watchdog: mpc %lld->%lld\n", ompc, adapter->stats.mpc);
>+ em_init_locked(adapter);
>+ }
> if (em_display_debug_stats && ifp->if_drv_flags & IFF_DRV_RUNNING) {
> em_print_hw_stats(adapter);
> }
>
>It helps to reduce downtime from few minutes to 2 seconds, but this
>is very dirty approach to the problem. Sample prints during runtime
>with patch:
>
>em watchdog: mpc 1767->2739
>em watchdog: mpc 2739->4724
>em watchdog: mpc 4724->7794
>em watchdog: mpc 7794->10729
>
>Every time this is printed, the network wedges for 2 seconds and then
>it revives.
>
>I am asking developers, who work in Intel, to pay attention to this problem.
>>From my side I can offer any help in testing and debugging.
>
>
>
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