[Samba] Huge number of small files performance regression from 3.5.16 to 4.6.5 with identical smb.conf

[Jeremy Allison]

On Tue, Jun 13, 2017 at 12:09:41PM +0200, awl1 via samba wrote:
> Hello Samba experts,
> 
> I have just successfully replaced the old default Thecus Samba
> version 3.5.16 on my Thecus NAS (32-bit Intel Atom, 3 GB RAM, i686
> Thecus kernel 2.6.33) by a current Samba 4.6.5 build that I have
> cross-compiled myself from scratch.
> 
> Note that so far, I am using the unchanged (i.e. exactly identical)
> old 3.5.16 smb.conf file for 4.6.5.
> 
> Everything seems to work fine in terms of functionality. From
> Windows PowerShell, I have been also able to verify with
> "Get-SmbConnection" that I am now using SMB3 ("dialect 3.1.1"), and
> I have noticed decent performance gains for copying large files as
> expected:
> 
>  * single large file copy, Win10 NTFS client to Thecus NAS ("write"):
>    before: Samba 3.5.16/SMB 1.5: ~18 MB per second
>    after: Samba 4.6.5/SMB 3.1.1: ~23 MB per second
> 
>  * single large file copy, Thecus NAS to Win10 NTFS client ("read"):
>    before: Samba 3.5.16/SMB 1.5: ~60 MB per second
>    after: Samba 4.6.5/SMB 3.1.1: ~85 MB per second
> 
> 
> But unfortunately, I have also run into a severe performance
> degradation for copying a huge number of small files between a Win10
> client and the NAS in both directions. My test scenario here is
> copying a single directory containing 5400 files of between less
> than 1kB and max 8kB in size in both directions (Win10 -> Thecus and
> the other way round).
> 
> To the best of my knowledge, performance-related parameters in
> smb.conf had already been tuned for 3.5.16 with good results - IIRC,
> it was especially crucial for write performance to switch from

Can you get comparitive wireshark traces for the two cases ?

That would help discover what the bottleneck is.