From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ie0-x22f.google.com (mail-ie0-x22f.google.com [IPv6:2607:f8b0:4001:c03::22f]) (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 C029A21F36A for ; Wed, 22 Apr 2015 14:02:34 -0700 (PDT) Received: by iebrs15 with SMTP id rs15so47327689ieb.3 for ; Wed, 22 Apr 2015 14:02:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:subject:from:to:cc:date:in-reply-to:references :content-type:mime-version:content-transfer-encoding; bh=zYWI7dtl9u7XDMIk5MnaZPolUiTdkMgXUASo/yLzAs8=; b=unpceT4j/d530LnJzwiYcH8RbCF7YYvncqpFRunEEn4JCUyji33KYXtI3mC1TiU7/f meDF8iLLKkd5okxjznGBDLY47AazzkWt1h3iZ+zft5zhTtHhRu63fJvhYWP1JFYEYdHT 5KQj19GYTSootrp9NAKsnd/0c97PttHlmgoZ+VTiLrnTN7AiD3wAHiR9DQ9+TVK25PkZ 56hGlpXBHPskPyAeKz1p4e8h4HMe22nGM//7OQp8xU+XH7c5U07JPk6Sr7tOK3J67NEU H2cOMyIzzS9ZmDfrpPV4/qPTSaez/QYkO4qm0lC81Z6wn5GMcHWkcGExEc73MD/LZqMe FCRw== X-Received: by 10.50.132.33 with SMTP id or1mr7460798igb.31.1429736553704; Wed, 22 Apr 2015 14:02:33 -0700 (PDT) Received: from [172.26.55.207] ([172.26.55.207]) by mx.google.com with ESMTPSA id to3sm7664299igb.1.2015.04.22.14.02.32 (version=TLSv1.2 cipher=AES128-GCM-SHA256 bits=128/128); Wed, 22 Apr 2015 14:02:33 -0700 (PDT) Message-ID: <1429736552.18561.144.camel@edumazet-glaptop2.roam.corp.google.com> From: Eric Dumazet To: Dave Taht Date: Wed, 22 Apr 2015 14:02:32 -0700 In-Reply-To: References: <20150422191056.9C7AC406057@ip-64-139-1-69.sjc.megapath.net> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Cc: Hal Murray , 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 21:03:03 -0000 Yeah, the real nice thing is TCP_NOTSENT_LOWAT added in linux-3.12 On Wed, 2015-04-22 at 12:28 -0700, Dave Taht wrote: > 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 wrote: > > > >> As I understand it (I thought) SO_SNDBUF and SO_RCVBUF are socket buffers > >> 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 larger > > 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 to > > what I expect but I haven't fired up tcpdump to verify that the window size > > is what I asked for. netperf does print out values that are 2x what I asked > > 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 > > >