[linux-cifs-client] extremely slow throughput writing to remote shares

[Christian Pernegger]

Hi all!

I regularly need to copy a bunch of large files (~150MB-1GB) to a CIFS
share (on a samba server). The machines are connected by a
consumer-grade Gbit network, which get ~540mbps in NPtcp and nearly
that on FTP transfers (as long as the files fit in the destination's
cache).

Problem is, the cifs performance is horrible. I get a little under
6MB/s, which is not quite the sustained writing speed of the target
disk's RAID-5 (8 MB/s). This leads me to believe that the recieving
side does not cache or is forced to sync continually.

Just to rule out the samba server I mounted a Windows (XPsp2) share
the same way, and it behaves likewise: 14MB/s (sustained write of the
disk a little over 20MB/s)

Tested by copying a 512MB test file (dded from /dev/zero), that was
bound to fit in cache.

In the past I've used gnome-vfs to do the copying, but testing was
done with mount -t cifs. No change with mount -t smbfs, if there even
is a difference.

Copying to the same server(s) from Windows clients is fine.

I can't offer any hints as to when it broke, I recently had to replace
the motherboard and NIC of the machine, along with an update of Debian
testing.

Both server and client use samba packages version 3.0.22-1 (probably
those aren't even involved), the client has the stock Debian testing
kernel (2.6.15 atm)

Thanks,

C.