From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-x22b.google.com (mail-ob0-x22b.google.com [IPv6:2607:f8b0:4003:c01::22b]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id AEB1F21F324 for ; Wed, 22 Apr 2015 12:28:51 -0700 (PDT) Received: by oblw8 with SMTP id w8so179131541obl.0 for ; Wed, 22 Apr 2015 12:28:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=DI9vxsZEFblFkex7kDuAQ/iP95CmrKTW2c8gjMwdK/Y=; b=rqEj4Ly5EnVFKi9i95WRd72NlvDJy424ynXxVQvv9FFOwNXHkpF/nDzF+QWXNjw+0Y 5q4KUI/Yn1rlG40X9wp9JRlXerYCPBP3gocchqKI/p//ZWL9hH7VGi4mminTYyU+CAV6 ppsht3yvJ0iI0T6QIJ1gsTuwwGhqdErlq6T/Wop8IVi8Dss/mVax5/t0+Ddbx3dHiArJ ag3q2iR3prr+JF47Tv+eA9rT3p4lDljUNxUVhjoscz2GPVj20EX8KQf8ImJmZJVTfjbf x6gaacFW7b7XycAB1VA7M4d1mtGHLUB6X7FeeM78FANyKBH4LMSXvcBnaUsjryg8unnN gsyg== MIME-Version: 1.0 X-Received: by 10.182.78.101 with SMTP id a5mr24883470obx.45.1429730930415; Wed, 22 Apr 2015 12:28:50 -0700 (PDT) Received: by 10.202.71.139 with HTTP; Wed, 22 Apr 2015 12:28:50 -0700 (PDT) In-Reply-To: <20150422191056.9C7AC406057@ip-64-139-1-69.sjc.megapath.net> References: <20150422191056.9C7AC406057@ip-64-139-1-69.sjc.megapath.net> Date: Wed, 22 Apr 2015 12:28:50 -0700 Message-ID: From: Dave Taht To: Hal Murray Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Cc: bloat Subject: Re: [Bloat] SO_SNDBUF and SO_RCVBUF X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 22 Apr 2015 19:29:20 -0000 SO_SNDLOWAT or something similar to it with a name I cannot recall, can be useful. On Wed, Apr 22, 2015 at 12:10 PM, Hal Murray wrot= e: > >> As I understand it (I thought) SO_SNDBUF and SO_RCVBUF are socket buffer= s >> for the application layer, they do not change the TCP window size either >> send or receive. Which is perhaps why they aren't used much. They don't = do >> much good in iperf that's for sure! Might be wrong, but I agree with the >> premise - auto-tuning should work. > > I sure expect them to do the obvious thing. > > man 7 socket says: > > SO_SNDBUF > Sets or gets the maximum socket send buffer in bytes. > > It doesn't actually say that turns into the TCP window size. > > On Linux, there is a factor of 2 for overhead and whatever. > > man tcp says: > TCP uses the extra space for administrative purposes and inter- > nal kernel structures, and the /proc file values reflect the l= arger > sizes compared to the actual TCP windows. > > So it looks like the number you feed it turns into the window size. > > A few quick tests with netperf confirm that it is doing something close t= o > what I expect but I haven't fired up tcpdump to verify that the window si= ze > is what I asked for. netperf does print out values that are 2x what I as= ked > for. > > Yuck. (That's Yuck at Linux, not netperf.) > > > -- > These are my opinions. I hate spam. > > > > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat --=20 Dave T=C3=A4ht Open Networking needs **Open Source Hardware** https://plus.google.com/u/0/+EricRaymond/posts/JqxCe2pFr67