Steve Wray
2008-Apr-23 02:32 UTC
[Xen-users] massive packet loss under network and disk load
As mentioned on a post to a thread about drbd and Xen I''ve been seeing
some horrific packet loss under network and disk IO load which has been
causing huge problems for drbd syncing and replication.
After testing many parameters and settings I have found that this
appears to make the problem go away:
vif = [
''rate=20MB/s,mac=AA:01:06:6D:FD:02, bridge=xenbr2''
]
''this'' being the ''rate=20MB/s''.
I''m not sure if this is merely brushing the problem under the carpet
but, all other things being at default settings, adding and removing the
rate option from the vif reliably makes the problem go away or come back.
The thing that worries me is that even with this parameter on the vif I
still see what I''d call massive packet loss on the vif for this domU as
seen in xm top.
All the dropped packets are RX
It looks like this:
Net0 RX: 544045974bytes 6253667pkts 0err 52645drop TX:
334397858bytes 3644125pkts
I hope that I am interpreting this correctly, that the
''52645drop''
indicates RX packets dropped...
I am seeing hundreds of drops per second.
Within the domU, ifconfig shows no dropped packets or errors.
On dom0, ifconfig shows TX packets dropped:
vif2.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF
inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link
UP BROADCAST RUNNING NOARP MTU:1500 Metric:1
RX packets:4187429 errors:0 dropped:0 overruns:0 frame:0
TX packets:7189734 errors:0 dropped:60679 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:383941238 (366.1 MiB) TX bytes:1911795684 (1.7 GiB)
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Ryan Burke
2008-Apr-23 12:18 UTC
Re: [Xen-users] massive packet loss under network and disk load
> As mentioned on a post to a thread about drbd and Xen I''ve been seeing > some horrific packet loss under network and disk IO load which has been > causing huge problems for drbd syncing and replication. > > After testing many parameters and settings I have found that this > appears to make the problem go away: > > vif = [ > ''rate=20MB/s,mac=AA:01:06:6D:FD:02, bridge=xenbr2'' > ] > > ''this'' being the ''rate=20MB/s''. > > I''m not sure if this is merely brushing the problem under the carpet > but, all other things being at default settings, adding and removing the > rate option from the vif reliably makes the problem go away or come back. > > The thing that worries me is that even with this parameter on the vif I > still see what I''d call massive packet loss on the vif for this domU as > seen in xm top. > > All the dropped packets are RX > > It looks like this: > > Net0 RX: 544045974bytes 6253667pkts 0err 52645drop TX: > 334397858bytes 3644125pkts > > I hope that I am interpreting this correctly, that the ''52645drop'' > indicates RX packets dropped... > > I am seeing hundreds of drops per second. > > Within the domU, ifconfig shows no dropped packets or errors. > > On dom0, ifconfig shows TX packets dropped: > > vif2.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF > inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link > UP BROADCAST RUNNING NOARP MTU:1500 Metric:1 > RX packets:4187429 errors:0 dropped:0 overruns:0 frame:0 > TX packets:7189734 errors:0 dropped:60679 overruns:0 carrier:0 > collisions:0 txqueuelen:0 > RX bytes:383941238 (366.1 MiB) TX bytes:1911795684 (1.7 GiB) >Just out of curiosity have you disabled TX checksums? I didn''t follow your previous thread so I don''t know that others had suggested. Try "ethtool - K eth0 tx off" and see if that helps your TX packet loss. Ryan _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Steve Wray
2008-Apr-23 19:56 UTC
Re: [Xen-users] massive packet loss under network and disk load
Ryan Burke wrote:>> As mentioned on a post to a thread about drbd and Xen I''ve been seeing >> some horrific packet loss under network and disk IO load which has been >> causing huge problems for drbd syncing and replication.[snip]> > Just out of curiosity have you disabled TX checksums? I didn''t follow your > previous thread so I don''t know that others had suggested. Try "ethtool - > K eth0 tx off" and see if that helps your TX packet loss.Yes that was among the options I tested and it made no difference. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users