From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cassarossa.samfundet.no (cassarossa.samfundet.no [IPv6:2001:67c:29f4::29]) (using TLSv1 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (Client did not present a certificate) by huchra.bufferbloat.net (Postfix) with ESMTPS id 337D321F2CE for ; Tue, 21 Apr 2015 21:05:00 -0700 (PDT) Received: from pannekake.samfundet.no ([2001:67c:29f4::50] ident=unknown) by cassarossa.samfundet.no with esmtps (TLS1.2:DHE_RSA_AES_128_CBC_SHA1:128) (Exim 4.80) (envelope-from ) id 1YkluA-0005VH-Al; Wed, 22 Apr 2015 06:04:55 +0200 Received: from sesse by pannekake.samfundet.no with local (Exim 4.80) (envelope-from ) id 1YkluA-0002nl-3y; Wed, 22 Apr 2015 06:04:54 +0200 Date: Wed, 22 Apr 2015 06:04:54 +0200 From: "Steinar H. Gunderson" To: jb Message-ID: <20150422040453.GB36239@sesse.net> References: <75C1DDFF-FBD2-4825-A167-92DFCF6A7713@gmail.com> <8AD4493E-EA21-496D-923D-B4257B078A1C@gmx.de> <8E4F61CA-4274-4414-B4C0-F582167D66D6@gmx.de> <2C987A4B-7459-43C1-A49C-72F600776B00@gmail.com> <14cd9e74e48.27f7.e972a4f4d859b00521b2b659602cb2f9@superduper.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Operating-System: Linux 3.18.4 on a x86_64 User-Agent: Mutt/1.5.21 (2010-09-15) Cc: bloat Subject: Re: [Bloat] DSLReports Speed Test has latency measurement built-in 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 04:05:29 -0000 On Tue, Apr 21, 2015 at 08:35:21PM +1000, jb 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. I haven't gone into the code and checked, but from practical experience I think you're wrong. I've certainly seen positive effects (and verified with tcpdump) from reducing SO_SNDBUF on a server that should have no problems at all sending data really fast to the kernel. Then again, this kind of manual tuning trickery got obsolete for me the moment sch_fq became available. /* Steinar */ -- Homepage: http://www.sesse.net/