From owner-freebsd-net@FreeBSD.ORG Sat May 4 20:47:27 2013 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115]) by hub.freebsd.org (Postfix) with ESMTP id 2A7C63D7; Sat, 4 May 2013 20:47:27 +0000 (UTC) (envelope-from jfvogel@gmail.com) Received: from mail-vc0-f173.google.com (mail-vc0-f173.google.com [209.85.220.173]) by mx1.freebsd.org (Postfix) with ESMTP id CCBABEE0; Sat, 4 May 2013 20:47:26 +0000 (UTC) Received: by mail-vc0-f173.google.com with SMTP id ht11so2291487vcb.32 for ; Sat, 04 May 2013 13:47:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:x-received:in-reply-to:references:date:message-id :subject:from:to:cc:content-type; bh=TOtLyy4iE7FjUnVSzy6OPY4Vx0uEVZe/R5FZO9iZNjQ=; b=lIsvCR1ROVcSZKOx+FMLSp+01b+2qibuqwSVDOidH+XmL9KrsCFQdpwIf0OYZyqlcY gU1kextqtkx4YlF6Kx2AY78vljfUm74gjp/w5PPgtmL6K4X/fQsuFCzaYuZiYP2VZmtj FVcc67vdhD1q5c3wkoApMQkjmW1tQnHRdI+3h6FNfAzl+IrGXMSqE3ArSsyfpmcL7j6y pVnMOTVbdDIim402jyP8FWodCIKeGyz4H+mgFtBFRG+M0/bNZNE10H55J5BY4N0cAY2f N/8lKQDt5LolyRwSXh1xgE+EGbWbIE3u8wtiZKEFtsnDmaO7mg6Z4C/FxsT3IUL/E+rJ nGyw== MIME-Version: 1.0 X-Received: by 10.52.122.18 with SMTP id lo18mr4377295vdb.32.1367700440537; Sat, 04 May 2013 13:47:20 -0700 (PDT) Received: by 10.220.55.143 with HTTP; Sat, 4 May 2013 13:47:20 -0700 (PDT) In-Reply-To: References: Date: Sat, 4 May 2013 13:47:20 -0700 Message-ID: Subject: Re: Is there any way to limit the amount of data in an mbuf chain submitted to a driver? From: Jack Vogel To: Richard Sharpe Content-Type: text/plain; charset=Big5 Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.14 Cc: FreeBSD Net , Adrian Chadd X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 04 May 2013 20:47:27 -0000 Yes, I checked: #define IXGBE_TSO_SIZE 262140 So, the driver is not limiting you to 64K assuming you are using a version of recent vintage. Jack On Sat, May 4, 2013 at 1:41 PM, Jack Vogel wrote: > If you don't use TSO you will hurt your TX performance significantly from > the tests that I've run. What exactly is the device you are using, I don'= t > have the source in front of me now, but I'm almost sure that the limit is > not 64K but 256K, or are you using some ancient version of the driver? > > Jack > > > > On Sat, May 4, 2013 at 1:30 PM, Richard Sharpe < > realrichardsharpe@gmail.com> wrote: > >> On Sat, May 4, 2013 at 10:39 AM, Adrian Chadd wrote= : >> > On 4 May 2013 06:52, Richard Sharpe >> wrote: >> >> Hi folks, >> >> >> >> I understand better why I am seeing EINVAL intermittently when sendin= g >> >> data from Samba via SMB2. >> >> >> >> The ixgbe driver, for TSO reasons, limits the amount of data that can >> >> be DMA'd to 65535 bytes. It returns EINVAL for any mbuf chain larger >> >> than that. >> >> >> >> The SO_SNDBUF for that socket is set to 131972. Mostly there is less >> >> than 64kiB of space available, so that is all TCP etc can put into th= e >> >> socket in one chain of mbufs. However, every now and then there is >> >> more than 65535 bytes available in the socket buffers, and we have an >> >> SMB packet that is larger than 65535 bytes, and we get hit. >> >> >> >> To confirm this I am going to set SO_SNDBUF back to the default of >> >> 65536 and test again. My repros are very reliable. >> >> >> >> However, I wondered if my only way around this if I want to continue >> >> to use SO_SNDBUF sizes larger than 65536 is to fragment large mbuf >> >> chains in the driver? >> > >> > Hm, is this is a problem without TSO? >> >> We are using the card without TSO, so I am thinking of changing that >> limit to 131072 and retesting. >> >> I am currently testing with SO_SNDBUF=3D32768 and have not hit the probl= em. >> >> > Is the problem that the NIC can't handle a frame that big, or a buffer >> that big? >> > Ie - if you handed the hardware two descriptors of 64k each, for the >> > same IP datagram, will it complain? >> >> I can't find any documentation, but it seems that with TSO it cannot >> handle a frame that big. Actually, since we are not using TSO, there >> really should not be a problem with larger frames. >> >> > Or do you need to break it up into two separate IP datagrams, facing >> > the driver, with a maximum size of 64k each? >> >> Not sure, but it looks like we need to do that. >> >> >> -- >> Regards, >> Richard Sharpe >> (=A6=F3=A5H=B8=D1=BC~=A1H=B0=DF=A6=B3=A7=F9=B1d=A1C--=B1=E4=BE=DE) >> _______________________________________________ >> freebsd-net@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-net >> To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" > > >