[linux-cifs-client] CIFS slow on gigabit, doesn't support sockopt=TCP_NODELAY ?

[Jeff Layton]

On Mon, 24 Aug 2009 14:36:37 -0400
Timothy Normand Miller <theosib at gmail.com> wrote:

> On Mon, Aug 24, 2009 at 9:50 AM, Jeff Layton<jlayton at redhat.com> wrote:
> > On Sun, 23 Aug 2009 20:21:10 -0400
> > Timothy Normand Miller <theosib at gmail.com> wrote:
> >
> >> Hi, everyone.
> >>
> >> I've noticed that the cifs client for Linux is slow over gigabit
> >> ethernet.  It seems to max out at about 10 megs/sec, while the drives
> >> can go a lot faster.  Also, if I mount the same network share from a
> >> Mac, it's a lot faster.  When _sharing_ via samba, one can set the
> >> TCP_NODELAY option (among others), which fixes the problem.  But with
> >> the cifs client, I find that there appears to be no way to set the
> >> option.  When mounting manually, you can use "-o sockopt=TCP_NODELAY",
> >> and you can also put that into /etc/fstab.  Either way, the option
> >> appears to be ignored.
> >>
> >
> > Yeah. The sockopt= option is completely ignored. I proposed a patch
> > to remove it not too long ago...
> >
> > I'm unclear...so you're saying here that turning on TCP_NODELAY on the
> > server it helps throughput when using the Linux CIFS client?
> 
> No.  I think I'll give you excess detail just to make sure that I
> don't leave out something important.  :)
> 
> I have a Linux server, an Apple AEBS with disks hanging off of it, and
> various clients (some Macs).  On the Linux server, I can configure the
> SMB server to enable those options so that when a client accesses the
> server, it's fast.  The AEBS is also a server, but I cannot configure
> it with those options.  I can get a Mac to get fast access to the AEBS
> by configuring those TCP options on the client side.
> 
> The problem pertains to having the Linux box access the disks on the
> AEBS.  In that case, I can't configure the TCP options on either the
> client (the Linux box in this case) or the server (the AEBS), so
> transfers are slow.  This is important, because a large part of my
> large file copies are between the Linux box and the AEBS.
> 
> On the Linux server, SMB configuration has no impact on CIFS performance.
>

If you wanted to experiment with it, it doesn't sound too hard to hack
up a patch to do so. You'd just need to add a kernel_setsockopt call to
the ipv4_connect (and/or ipv6_connect) functions. The place where the
sk_rcvtimeo/sk_sndtimeo get set is probably around the right spot. In
fact, those should probably be changed to kernel_setsockopt calls too.

If that shows notable improvement then we could discuss the best way to
set up an option for it. Probably we'd want to flesh out the sockopt=
option.

-- 
Jeff Layton <jlayton at redhat.com>