[Samba] aio settings for samba 4.3

[Jeremy Allison]

On Thu, Jul 21, 2016 at 10:50:16PM +0200, Achim Gottinger wrote:
> 
> 
> Am 21.07.2016 um 20:56 schrieb Russell R Poyner:
> >Jeremy,
> >
> >I think this is exactly a complex interaction between FreeBSD and
> >Samba. Best guess would be some system call that is fast in linux
> >but slow in FreeBSD holding things back.
> >
> >Russ
> >
> >On 07/21/2016 01:00 PM, Jeremy Allison wrote:
> >>On Thu, Jul 21, 2016 at 12:23:01PM -0500, Russell R Poyner wrote:
> >>>One more data point for comparison
> >>>
> >>>I installed the stock samba 4.2 rpm on a centos 7 machine and ran
> >>>the same diskspd tests against a share configured with:
> >>>    vfs objects = aio_pthread
> >>>    aio read size = 1024
> >>>    aio read size = 1024
> >>>
> >>>    smb2 leases = yes
> >>>
> >>>I get 27MB/s with 4k blocks and 145MB/s with 64k blocks. Disabling
> >>>cacheing by passing the -h switch to diskspd lowered these to 72MB/s
> >>>and 11MB/s. Which I view as 'close enough' to wire speed. Thus it
> >>>seems that the dismal performance I see is associated with the
> >>>FreeBSD implementation somehow.
> >>That's interesting, but I'm afraid I don't know FreeBSD well
> >>enough to help here. This does imply the problem isn't Samba
> >>specific though (unless it's a complex interaction between
> >>Samba+FreeBSD).
> >
> >
> On my debian jessie server with zfs these settings seem to work.
> 
> max xmit = 65536
> socket options = TCP_NODELAY
> 
> Copying an file from server to a windows 7 client increases from 50%
> to 80% network utilisation on an  1GB link without jumbo frames when
> i add these settings.

That's kind of voodoo I'm afraid. By default Samba sets
TCP_NODELAY, and max xmit is only used on SMB1, and modern
Samba and Windows 7 should only be using SMB2.