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Re: [Xen-devel] tx offload issue w/stubdoms + igb

To: John Weekes <lists.xen@xxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] tx offload issue w/stubdoms + igb
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Tue, 14 Dec 2010 14:00:47 -0800
Cc: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxx>, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
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(Added Stefano.)

On 12/14/2010 01:59 PM, Jeremy Fitzhardinge wrote:
> On 12/14/2010 02:12 AM, John Weekes wrote:
>> I tested further and found that:
>>
>> * dom0 does't have the issue, normal PV domains do not have the issue,
>> and Windows GPLPV-based domains do not have the issue. It seems to be
>> specific to stubdom-based domains.
> That's interesting.  There were a number of fixes to netfront/back to
> make sure all this checksum offload stuff worked properly, and I was
> never convinced they were also ported to stubdom's netfront.  I don't
> remember the specifics now, unfortunately.
>
>     J
>
>> * Other machines running the exact same Xen release and kernel
>> version, but that use the e1000 driver instead of the igb driver,
>> don't seem to have the problem. I don't know if it's related (I have
>> not yet been able to test with MSI disabled), but those machines
>> without the problem also aren't using MSI-X, whereas the igb-based
>> machine that shows the problem is. From dmesg:
>>
>> [   21.209923] Intel(R) Gigabit Ethernet Network Driver - version
>> 1.3.16-k2
>> [   21.210026] Copyright (c) 2007-2009 Intel Corporation.
>> [   21.210140] xen: registering gsi 28 triggering 0 polarity 1
>> [   21.210145] xen: --> irq=28
>> [   21.210151] igb 0000:01:00.0: PCI INT A -> GSI 28 (level, low) ->
>> IRQ 28
>> [   21.210279] igb 0000:01:00.0: setting latency timer to 64
>> [   21.382336] igb 0000:01:00.0: Intel(R) Gigabit Ethernet Network
>> Connection
>> [   21.382435] igb 0000:01:00.0: eth0: (PCIe:2.5Gb/s:Width x4)
>> 00:25:90:09:e4:00
>> [   21.382605] igb 0000:01:00.0: eth0: PBA No: ffffff-0ff
>> [   21.382698] igb 0000:01:00.0: Using MSI-X interrupts. 4 rx
>> queue(s), 4 tx queue(s)
>>
>> (Both the e1000 and igb machines have the hvm_directio flag in the "xl
>> info" output.)
>>
>> * Different GSO/TSO settings do not appear to make a difference. Only
>> the tx offload setting does.
>>
>> * Inside the problematic domU, the bad segment counter increments when
>> the issue is occurring:
>>
>> testvds5 ~ # netstat -s eth0
>> Ip:
>>     22162 total packets received
>>     44 with invalid addresses
>>     0 forwarded
>>     0 incoming packets discarded
>>     22113 incoming packets delivered
>>     19582 requests sent out
>> Icmp:
>>     2694 ICMP messages received
>>     0 input ICMP message failed.
>>     ICMP input histogram:
>>         timeout in transit: 2447
>>         echo replies: 247
>>     2698 ICMP messages sent
>>     0 ICMP messages failed
>>     ICMP output histogram:
>>         destination unreachable: 2
>> IcmpMsg:
>>         InType0: 247
>>         InType11: 2447
>>         OutType3: 2
>>         OutType69: 2696
>> Tcp:
>>     4 active connections openings
>>     3 passive connection openings
>>     0 failed connection attempts
>>     0 connection resets received
>>     3 connections established
>>     18819 segments received
>>     16795 segments send out
>>     0 segments retransmited
>>     2366 bad segments received.
>>     8 resets sent
>> Udp:
>>     65 packets received
>>     2 packets to unknown port received.
>>     0 packet receive errors
>>     89 packets sent
>> UdpLite:
>> TcpExt:
>>     1 TCP sockets finished time wait in fast timer
>>     172 delayed acks sent
>>     Quick ack mode was activated 89 times
>>     3 packets directly queued to recvmsg prequeue.
>>     33304 bytes directly in process context from backlog
>>     3 bytes directly received in process context from prequeue
>>     7236 packet headers predicted
>>     23 packets header predicted and directly queued to user
>>     3117 acknowledgments not containing data payload received
>>     89 DSACKs sent for old packets
>>     2 DSACKs sent for out of order packets
>>     2 connections reset due to unexpected data
>> IpExt:
>>     InBcastPkts: 533
>>     InOctets: 23420805
>>     OutOctets: 1601733
>>     InBcastOctets: 162268
>> testvds5 ~ #
>>
>> * Some sites transfer quickly to the domU quickly regardless of the tx
>> offload setting, exhibiting the symptoms less. For instance, uiuc.edu
>> with tx on:
>>
>> root@testvds5:~# wget
>> http://gentoo.cites.uiuc.edu/pub/gentoo/releases/amd64/10.1/livedvd-amd64-multilib-10.1.iso
>> --2010-12-14 03:53:50-- 
>> http://gentoo.cites.uiuc.edu/pub/gentoo/releases/amd64/10.1/livedvd-amd64-multilib-10.1.iso
>> Resolving gentoo.cites.uiuc.edu... 128.174.5.78
>> Connecting to gentoo.cites.uiuc.edu|128.174.5.78|:80... connected.
>> HTTP request sent, awaiting response... 200 OK
>> Length: 2798649344 (2.6G) [text/plain]
>> Saving to: `livedvd-amd64-multilib-10.1.iso'
>>
>>  0% [                                       ] 25,754,272  3.06M/s  eta
>> 17m 7s  ^C
>> root@testvds5:~#
>>
>> (netstat shows 23 bad segments received over the length of that test)
>>
>> and with tx off:
>>
>> root@testvds5:~# wget
>> http://gentoo.cites.uiuc.edu/pub/gentoo/releases/amd64/10.1/livedvd-amd64-multilib-10.1.iso
>> --2010-12-14 03:54:45-- 
>> http://gentoo.cites.uiuc.edu/pub/gentoo/releases/amd64/10.1/livedvd-amd64-multilib-10.1.iso
>> Resolving gentoo.cites.uiuc.edu... 128.174.5.78
>> Connecting to gentoo.cites.uiuc.edu|128.174.5.78|:80... connected.
>> HTTP request sent, awaiting response... 200 OK
>> Length: 2798649344 (2.6G) [text/plain]
>> Saving to: `livedvd-amd64-multilib-10.1.iso.1'
>>
>>  1% [                                       ] 47,677,960  3.95M/s  eta
>> 12m 0s  ^C
>>
>> * The issue also occurs in xen-4.0-testing, as of c/s 21392.
>>
>> For reference, Xen and kernel version output:
>>
>> nyc-dodec266 src # xl info
>> host                   : nyc-dodec266
>> release                : 2.6.32.26-g862ef97
>> version                : #4 SMP Wed Dec 8 16:38:18 EST 2010
>> machine                : x86_64
>> nr_cpus                : 24
>> nr_nodes               : 2
>> cores_per_socket       : 12
>> threads_per_core       : 1
>> cpu_mhz                : 2674
>> hw_caps                :
>> bfebfbff:2c100800:00000000:00003f40:029ee3ff:00000000:00000001:00000000
>> virt_caps              : hvm hvm_directio
>> total_memory           : 49143
>> free_memory            : 9178
>> free_cpus              : 0
>> xen_major              : 4
>> xen_minor              : 1
>> xen_extra              : -unstable
>> xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32
>> hvm-3.0-x86_32p hvm-3.0-x86_64
>> xen_scheduler          : credit
>> xen_pagesize           : 4096
>> platform_params        : virt_start=0xffff800000000000
>> xen_changeset          : Wed Dec 08 10:46:31 2010 +0000
>> 22467:89116f28083f
>> xen_commandline        : dom0_mem=2550M dom0_max_vcpus=4
>> cc_compiler            : gcc version 4.4.4 (Gentoo 4.4.4-r2 p1.2,
>> pie-0.4.5)
>> cc_compile_by          : root
>> cc_compile_domain      : nuclearfallout.net
>> cc_compile_date        : Fri Dec 10 00:51:50 EST 2010
>> xend_config_format     : 4
>> nyc-dodec266 src # uname -a
>> Linux nyc-dodec266 2.6.32.26-g862ef97 #4 SMP Wed Dec 8 16:38:18 EST
>> 2010 x86_64 Intel(R) Xeon(R) CPU X5650 @ 2.67GHz GenuineIntel GNU/Linux
>>
>> For now, I can use the "tx off" workaround by having a script set it
>> for all newly created domains. Is anyone up for nailing this down and
>> finding a real fix? Failing that, applying the workaround in the Xen
>> tools might be a good idea.
>>
>> -John
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>> http://lists.xensource.com/xen-devel
>>


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