Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932614Ab1ESGgP (ORCPT ); Thu, 19 May 2011 02:36:15 -0400 Received: from mta-1.ms.rz.RWTH-Aachen.DE ([134.130.7.72]:46928 "EHLO mta-1.ms.rz.rwth-aachen.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932079Ab1ESGgN (ORCPT ); Thu, 19 May 2011 02:36:13 -0400 MIME-version: 1.0 X-IronPort-AV: E=Sophos;i="4.65,235,1304287200"; d="sig'?scan'208";a="55171079" Subject: Re: [PATCH] tcp: Implement a two-level initial RTO as per draft RFC 2988bis-02. Content-type: multipart/signed; protocol="application/pgp-signature"; micalg=pgp-sha1; boundary=Apple-Mail-34-1062255599 From: Alexander Zimmermann In-reply-to: Date: Thu, 19 May 2011 08:36:09 +0200 Cc: David Miller , kuznet@ms2.inr.ac.ru, pekkas@netcore.fi, jmorris@namei.org, yoshfuji@linux-ipv6.org, kaber@trash.net, hagen@jauu.net, eric.dumazet@gmail.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Content-transfer-encoding: 7bit Message-id: References: <1305771744-83951-1-git-send-email-tsunanet@gmail.com> <20110518.223622.1525088601595365235.davem@davemloft.net> <20110519.001426.2119532755281545481.davem@davemloft.net> <9DC9A4D5-8E16-4361-B323-C92D563171A1@comsys.rwth-aachen.de> To: tsuna X-Pgp-Agent: GPGMail 1.3.3 X-Mailer: Apple Mail (2.1084) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3539 Lines: 96 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --Apple-Mail-34-1062255599 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii Am 19.05.2011 um 08:25 schrieb tsuna: > On Wed, May 18, 2011 at 11:10 PM, Alexander Zimmermann > wrote: >> Am 19.05.2011 um 06:33 schrieb tsuna: >>> Presumably if the user decides to tweak these knobs, they'll know >>> what's appropriate for their environment. >> >> Are you sure? I'm not. I fully agree with David that minRTO is > > s/minRTO/initRTO/, right? Yes of course :-) > >> something that a user shout not control at all > > I personally don't like to hold the hand and spoon feed users too > much, I want to trust them to be responsible and know what they're > doing. Yes, there will always be people who will act stupid and do > stupid things with whatever knobs you expose. The web is full of > people who advise to tune up all the TCP rmem/wmem parameters to crazy > high level based on the voodoo belief that they're going to improve > their TCP performance, but then as long as you have knobs in your > system, these people will misuse them anyway and shoot themselves in > the foot, what can we do about that. But if you tune rmen/wmen to crazy level, it's only your TCP performance that hurts (and maybe the receiver's one). If you set the initRTO=0.1s, it's good for me but bad for the rest of the world. That's the difference. Or do you want to implement a lower barrier of 1sec so that you can ensure that nobody set the initRTO lower than 1s? > > There's also a good chunk of people who know what they're doing, and > for them compile-time constants are annoying because it's inconvenient > to experiment and iterate quickly when you need to recompile your > kernel to change a value. If turning the compile time constant into a > knob leaves the code reasonably straightforward and doesn't incur too > much overhead, then why not do it? > > Regarding this knob in particular, I can imagine that people who are > in environment where RTT easily gets around 1s will be upset by the > change in the default value, and doubly upset that they have to > recompile their kernel to change the value back to 3s. I'm in favor > of the reduction of initRTO, for the same reason Google is, but I can > also understand that the direction we're taking might not be > appropriate for everyone. > > -- > Benoit "tsuna" Sigoure > Software Engineer @ www.StumbleUpon.com // // Dipl.-Inform. Alexander Zimmermann // Department of Computer Science, Informatik 4 // RWTH Aachen University // Ahornstr. 55, 52056 Aachen, Germany // phone: (49-241) 80-21422, fax: (49-241) 80-22222 // email: zimmermann@cs.rwth-aachen.de // web: http://www.umic-mesh.net // --Apple-Mail-34-1062255599 content-type: application/pgp-signature; x-mac-type=70674453; name=PGP.sig content-description: Signierter Teil der Nachricht content-disposition: inline; filename=PGP.sig content-transfer-encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.17 (Darwin) Comment: GPGTools - http://gpgtools.org iEYEARECAAYFAk3UuloACgkQdyiq39b9uS4u+QCgkTNKQJta2KV8HJvVM95Q0/vH rNAAoIa+QlC5gNgk5T9b1K2VsE5LT12S =fMU8 -----END PGP SIGNATURE----- --Apple-Mail-34-1062255599-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/