From: "Myklebust, Trond" <Trond.Myklebust@netapp.com>
To: "J. Bruce Fields" <bfields@fieldses.org>
CC: Ben Myers <bpm@sgi.com>, Olga Kornievskaia <aglo@citi.umich.edu>,
        "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>,
        Jim Rees <rees@umich.edu>
Subject: RE: sunrpc: socket buffer size tuneable
Date: Fri, 25 Jan 2013 21:45:12 +0000
Message-ID: <4FA345DA4F4AE44899BD2B03EEEC2FA91833BFFE@sacexcmbx05-prd.hq.netapp.com>
References: <20130125192935.GA32470@sgi.com>
 <20130125202107.GD29596@fieldses.org> <20130125203507.GW30652@sgi.com>
 <4FA345DA4F4AE44899BD2B03EEEC2FA91833BF5A@sacexcmbx05-prd.hq.netapp.com>
 <20130125212106.GH29596@fieldses.org>
 <4FA345DA4F4AE44899BD2B03EEEC2FA91833BFAB@sacexcmbx05-prd.hq.netapp.com>
 <20130125213503.GI29596@fieldses.org>
In-Reply-To: <20130125213503.GI29596@fieldses.org>
Content-Type: text/plain; charset="Windows-1252"
MIME-Version: 1.0
Sender: linux-nfs-owner@vger.kernel.org

> -----Original Message-----
> From: J. Bruce Fields [mailto:bfields@fieldses.org]
> Sent: Friday, January 25, 2013 4:35 PM
> To: Myklebust, Trond
> Cc: Ben Myers; Olga Kornievskaia; linux-nfs@vger.kernel.org; Jim Rees
> Subject: Re: sunrpc: socket buffer size tuneable
> 
> On Fri, Jan 25, 2013 at 09:29:09PM +0000, Myklebust, Trond wrote:
> > > -----Original Message-----
> > > From: J. Bruce Fields [mailto:bfields@fieldses.org]
> > > Sent: Friday, January 25, 2013 4:21 PM
> > > To: Myklebust, Trond
> > > Cc: Ben Myers; Olga Kornievskaia; linux-nfs@vger.kernel.org; Jim
> > > Rees
> > > Subject: Re: sunrpc: socket buffer size tuneable
> > >
> > > On Fri, Jan 25, 2013 at 09:12:55PM +0000, Myklebust, Trond wrote:
> >
> > > > Why is it not sufficient to clamp the TCP values of 'snd' and
> > > > 'rcv' using
> > > sysctl_tcp_wmem/sysctl_tcp_rmem?
> > > > ...and clamp the UDP values using
> > > sysctl_[wr]mem_min/sysctl_[wr]mem_max?.
> > >
> > > Yeah, I was just looking at that--so, Ben, something like:
> > >
> > > 	echo "1048576 1048576 4194304" >/proc/sys/net/ipv4/tcp_wmem
> > >
> > > But I'm unclear on some of the details: do we need to set the
> > > minimum or only the default?  And does it need any more allowance
> > > for protocol overhead?
> >
> > I meant adding a check either to svc_sock_setbufsize or to the 2 call-sites
> that enforces the above limits.
> 
> I lost you.
> 
> It's not svc_sock_setbufsize that's setting too-small values, if that's what you
> mean.
> 

I understood that the problem was svc_udp_recvfrom() and svc_setup_socket() were using negative values in the calls to svc_sock_setbufsize(). Looking again at svc_setup_socket(), I don't see how that could do so, but svc_udp_recvfrom() definitely has potential to cause damage.

The TCP layer should be taking care to always clamp the send/receive buffer sizes in tcp_new_space(),tcp_clamp_window(), etc...

Trond