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packet drops under vmware with newer kernels
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tazinblack
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Joined: 23 Jan 2005
Posts: 899
Location: Baden / Germany

PostPosted: Wed Aug 14, 2013 10:20 am    Post subject: packet drops under vmware with newer kernels Reply with quote

Hi together,

I have an issue with some virtual gentoo machines running on vmware esxi 5.1 using newer kernels.
I run i.e icinga on these vms which sends and receives a lot of small network packets as I think.
Problem is that aI have a lot of dropped incoming packets:

Code:
enp2s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet <some ip>  netmask 255.255.255.0  broadcast <some bc adress>
        inet6 <some mac address>  prefixlen 64  scopeid 0x20<link>
        ether <some mac address>  txqueuelen 1000  (Ethernet)
        RX packets 16357  bytes 1872630 (1.7 MiB)
        RX errors 0  dropped 545  overruns 0  frame 0
        TX packets 17015  bytes 7781044 (7.4 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0


As you can see I have 545 dropped RX packets and this VM is only running for about 5 minutes.
This number increases every minute. After some days I have millions of them.
I also have very poor check latency in icinga. It does not matter if I use e1000 driver based network
interface or vmxnet3. It's the same behavior on both of them.

Looks like this is with kernels greater 3.2 On machines using old 2.6 kernels I do not have this issue.
I also have a ubuntu vm using 3.2.0.29 kernel which also drops packages but there I have only about 5600 over 239 days uptime and that I think may be normal.
Another suse sles11 with kernel 2.6.27.19-5-default does not drop any packet.

I tried to extent RX buffer with ethtool -G enp2s0 rx 4096 so that I have these values configured:

Code:
ethtool -g enp2s0
Ring parameters for enp2s0:
Pre-set maximums:
RX:             4096
RX Mini:        0
RX Jumbo:       0
TX:             4096
Current hardware settings:
RX:             4096
RX Mini:        0
RX Jumbo:       0
TX:             256


But this does not change anything. I also can not see dropped packets on the virtual or any physical switch.
Would be great if anyone out there could give me a hint how to fix this. :wink:
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Neon Dude
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Joined: 13 Jun 2004
Posts: 15
Location: London

PostPosted: Thu Aug 15, 2013 8:10 pm    Post subject: Reply with quote

Hi,

So dropped packets can take quite some debugging, but you may want to try experimenting with the net.core.netdev_max_backlog sysctl setting - try bumping it up and see if this has any impact. It may also require net.core.rmem_max/net.core.wmem_max to be increased too.

Good luck!
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tazinblack
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PostPosted: Fri Aug 16, 2013 6:18 am    Post subject: Reply with quote

Good idea, thank you!

The defaults were
Code:
sysctl net.core
net.core.dev_weight = 64
net.core.message_burst = 10
net.core.message_cost = 5
net.core.netdev_budget = 300
net.core.netdev_max_backlog = 1000
net.core.netdev_tstamp_prequeue = 1
net.core.optmem_max = 20480
net.core.rmem_default = 212992
net.core.rmem_max = 212992
net.core.rps_sock_flow_entries = 0
net.core.somaxconn = 128
net.core.warnings = 1
net.core.wmem_default = 212992
net.core.wmem_max = 212992
net.core.xfrm_acq_expires = 30
net.core.xfrm_aevent_etime = 10
net.core.xfrm_aevent_rseqth = 2
net.core.xfrm_larval_drop = 1


And I changed them to

Code:
sysctl net.core
net.core.dev_weight = 64
net.core.message_burst = 10
net.core.message_cost = 5
net.core.netdev_budget = 300
net.core.netdev_max_backlog = 10000
net.core.netdev_tstamp_prequeue = 1
net.core.optmem_max = 20480
net.core.rmem_default = 212992
net.core.rmem_max = 425984
net.core.rps_sock_flow_entries = 0
net.core.somaxconn = 128
net.core.warnings = 1
net.core.wmem_default = 212992
net.core.wmem_max = 425984
net.core.xfrm_acq_expires = 30
net.core.xfrm_aevent_etime = 10
net.core.xfrm_aevent_rseqth = 2
net.core.xfrm_larval_drop = 1


I also tried to adjust settings recommended here http://gnet.soe.ucsc.edu/doku.php?id=tcptuning and here http://www.speedguide.net/articles/linux-tweaking-121.

Unfortunately this does not have any effect.

I have round about 1 dropped packed per second and nothing I try seems to help :-(
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tazinblack
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tazinblack
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Joined: 23 Jan 2005
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PostPosted: Thu Sep 19, 2013 10:59 am    Post subject: Reply with quote

isn't there anything new that can help?
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