samba - Sep 2016 - No increased throughput with SMB Multichannel and two NICs

On 06.09.2016 19:39, Jeremy Allison via samba wrote:
> On Tue, Sep 06, 2016 at 03:56:14PM +0200, Daniel Vogelbacher via samba
wrote:
>>
>> Am 2016-09-06 10:41, schrieb Anoop C S via samba:
>>> On Sun, 2016-09-04 at 11:42 +0200, Daniel Vogelbacher via samba
wrote:
>>>> Hello,
>>>>
>>>> I'm running Samba 4.4.5 with enabled SMB Multichannel. The
Linux
>>>> server
>>>> has two 1GBit/s NICs and for testing purposes I've shared a
tmpfs
>>>> mountpoint with 2GiB and ~2GiB large test-file.
>>>>
>>>> My Windows 10 host has one dual-port 1GBit/s NIC, and if both
>>>> interfaces
>>>> are enabled, Get-SmbMultichannelConnection lists active
multichannel
>>>> connections to my Linux SMB server.
>>>>
>>>> If I disable one NIC on Windows, the other NIC is used with
~1GBit/s
>>>> when transferring the test-file from Linux to Windows.
>>>> If I enable both NICs, instead of 2x1Gbit/s I only get
~500MBit/s per
>>>> interface (but both interfaces are used).
>>>>
>>>> So instead of doubling the throughput, traffic is split up
between
>>>> two
>>>> interface half by half.
>>>>
>>>
>>> This is mostly a Windows client-controlled behavior. Refer to the
>>> following reply for a thread on similar subject for more details. 
>>>
>>> https://lists.samba.org/archive/samba/2016-August/201841.html
>>
>>
>> [...]AFAIK, the windows client only puts traffic on interfaces of same
>> speed and quality simultaneouslt[...]
>>
>> I interpret this as "with two identical NIC-speeds at server-side
>> and client-side it should result in double throughput".
>> On both hosts I've 2x1GBit/s NICs and Windows uses both(!) NICs
(but
>> not at full speed when multichannel is enabled). So I don't think
my
>> problem is related to this thread, beacuse if it is, Windows would
>> choose only one NIC.
> 
> What do you have set for "aio read size"/"aio write
size"
> in your smb.conf ?
> 
I don't have these options in my smb.conf.
Do you recommend any specific values?


Regards
Daniel Vogelbacher

On Tue, Sep 06, 2016 at 07:58:27PM +0200, Daniel Vogelbacher via samba
wrote:
> I don't have these options in my smb.conf.
> Do you recommend any specific values?
aio read size = 1
aio write size = 1

You might try with current master. There we have improved async I/O
handling significantly.

Volker

On Tue, Sep 06, 2016 at 08:06:48PM +0200, Volker Lendecke via samba
wrote:
> On Tue, Sep 06, 2016 at 07:58:27PM +0200, Daniel Vogelbacher via samba
wrote:
> > I don't have these options in my smb.conf.
> > Do you recommend any specific values?
> 
> aio read size = 1
> aio write size = 1
> 
> You might try with current master. There we have improved async I/O
> handling significantly.
Yep. Without those values smbd reads/writes synchronously, meaning
issuing two requests down different TCP sockets still get serialized
in the server. With aio turned on they'll get handed to a pthread
pool to complete, allowing as many requests as your client will send
to be outstanding (and your disk and network bandwith will allow of
course :-).