TSO help or hindrance ? (was Re: TSO and FreeBSD vs Linux)

[Barney Cordoba]

Didn't read down far enough.  There are def issues and gains are probably mostly in a lab with  9k frames. Turn it off. CPUs and buses are fast. 

BC


On Sep 10, 2013, at 6:52 PM, Mike Tancsa <mike at sentex.net> wrote:

> On 9/10/2013 6:42 PM, Barney Cordoba wrote:
>> NFS has been broken since Day 1, so lets not come to conclusions about
>> anything
>> as it relates to NFS.
> 
> iSCSI is NFS ?
> 
>    ---Mike
> 
>> 
>> BC
>> 
>> ------------------------------------------------------------------------
>> *From:* Mike Tancsa <mike at sentex.net>
>> *To:* Rick Macklem <rmacklem at uoguelph.ca>
>> *Cc:* FreeBSD Net <net at freebsd.org>; David Wolfskill <david at catwhisker.org>
>> *Sent:* Wednesday, September 4, 2013 11:26 AM
>> *Subject:* TSO help or hindrance ? (was Re: TSO and FreeBSD vs Linux)
>> 
>> On 9/4/2013 8:50 AM, Rick Macklem wrote:
>>> David Wolfskill wrote:
>>>> 
>>>> 
>>>> I noticed that when I tried to write files to NFS, I could write
>>>> small
>>>> files OK, but larger ones seemed to ... hang.
>>>> * "ifconfig -v em0" showed flags TSO4 & VLAN_HWTSO turned on.
>>>> * "sysctl net.inet.tcp.tso" showed "1" -- enabled.
>>>> 
>>>> As soon as I issued "sudo net.inet.tcp.tso=0" ... the copy worked
>>>> without
>>>> a hitch or a whine.  And I was able to copy all 117709618 bytes, not
>>>> just
>>>> 2097152 (2^21).
>>>> 
>>>> Is the above expected?  It came rather as a surprise to me.
>>>> 
>>> Not surprising to me, I'm afraid. When there are serious NFS problems
>>> like this, it is often caused by a network fabric issue and broken
>>> TSO is at the top of the list w.r.t. cause.
>> 
>> 
>> I was just experimenting a bit with iSCSI via FreeNAS and was a little
>> disappointed at the speeds I was getting. So, I tried disabling tso on
>> both boxes and it did seem to speed things up a bit.  Data and testing
>> methods attached in a txt file.
>> 
>> I did 3 cases.
>> 
>> Just boot up FreeNAS and the initiator without tweaks.  That had the
>> worst performance.
>> disable tso on the nic as well as via sysctl on both boxes. That had the
>> best performance.
>> re-enable tso on both boxes. That had better performance than the first
>> case, but still not as good as totally disabling it.  I am guessing
>> something is not quite being re-enabled properly ? But its different
>> than the other two cases ?!?
>> 
>> tgt is FreeNAS-9.1.1-RELEASE-x64 (a752d35) and initiator is r254328 9.2
>> AMD64
>> 
>> The FreeNAS box has 16G of RAM, so the file is being served out of cache
>> as gstat shows no activity when sending out the file
>> 
>> 
>> 
>>    ---Mike
>> 
>> 
>> -- 
>> -------------------
>> Mike Tancsa, tel +1 519 651 3400
>> Sentex Communications, mike at sentex.net <mailto:mike at sentex.net>
>> Providing Internet services since 1994 www.sentex.net
>> Cambridge, Ontario Canada  http://www.tancsa.com/
>> 
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> 
> 
> -- 
> -------------------
> Mike Tancsa, tel +1 519 651 3400
> Sentex Communications, mike at sentex.net
> Providing Internet services since 1994 www.sentex.net
> Cambridge, Ontario Canada   http://www.tancsa.com/
> _______________________________________________
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