Samba 4 has high CPU usage when accessing mapped drive through Windows

Question

I have noticed that when I access my Samba share from Windows, the smbd daemon will always use aprox 10-20% CPU - no matter if the share is used or not from Windows. Even if I close the share/window, smbd will continue using CPU and only a reboot/shutdown of my Windows can get the CPU usage down to normal.

This is when I have just rebooted/started my Windows - the share is mapped but not accessed yet. It will have this "red" status in Windows until I access it:

Before I do anything else I check the smbstatus and top on my Linux:

There is no problem so far - the CPU usage is not noticable at all in top so everything is still good.

BUT ... when I then access the share from Windows, the Linux CPU immediately raises to 10-20%:

And the smbstatus always shows some locked(?) files which for sure(?) is not accessed from my Windows:

The testparm shows my smb.conf configuration:

The only way I can "fix this" is by either rebooting my Windows or unmap the drive/share.

One more strange thing - when I have unmapped the share/drive, I can of course still access the share via UNC... and when accessing it through UNC it does NOT raise the CPU at all!? Weird!

My hardware is quite recent/uptodate:

Server: Core i5 1.5-2.9GHz dual core/HT 16GB RAM Samsung 850 Pro (512GB)

Client: Windows 8.1

I have used the same configuration on a CentOS 6 installation without any problems. I have also tried disabling whatever I think can communicate with the network share on my Windows computer (antivirus and backup software).

Can anyone help nailing this problem down?

Solution

Possibly a bit late but I found this, while having a similar problem.

I have a Raspberry Pi B+ with samba configured as a drive store, with a direct connection to my laptop over Ethernet.

My setup is as follows:

• several external hard drives connected to raspberry pi.
• Raspberry pi uses direct Ethernet connection to my laptop.

I have found:

• high cpu usage by smbd when reading from external (45%)
• high cpu usage by mount.ntfs when writing to external (46%)

Considering specs of B+, it seems somewhat believable since a simple apt update takes a minute of so if just refreshing list...

This might make for some good reading

Comments

[Preexo]

I observe the same behavior on one of my samba servers, did you ever find an explanation for that and is it really abnormal?

[Michael D.]

If samba isn't the dance you want to dance use NFS. Linux/*nix native network fs and maybe a bit less resource hogging. superuser.com/questions/525473/…

[TCB13]

I've the same problem with macOS clients here.