From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [net-next PATCH 1/3] net: make default tx_queue_len configurable Date: Wed, 29 Jul 2015 14:37:31 -0700 (PDT) Message-ID: <20150729.143731.834219016906219771.davem@davemloft.net> References: <1438203103-27013-2-git-send-email-phil@nwl.cc> <20150729210618.GF32705@breakpoint.cc> <20150729213428.GC15554@orbit.nwl.cc> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: fw@strlen.de, netdev@vger.kernel.org, brouer@redhat.com, cwang@twopensource.com, eric.dumazet@gmail.com To: phil@nwl.cc Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:34318 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753264AbbG2Vhc (ORCPT ); Wed, 29 Jul 2015 17:37:32 -0400 In-Reply-To: <20150729213428.GC15554@orbit.nwl.cc> Sender: netdev-owner@vger.kernel.org List-ID: From: Phil Sutter Date: Wed, 29 Jul 2015 23:34:28 +0200 > On Wed, Jul 29, 2015 at 11:06:18PM +0200, Florian Westphal wrote: >> Phil Sutter wrote: > [...] >> > +config DEFAULT_TX_QUEUE_LEN >> > + prompt "Default TX queue length (in packets)" if EXPERT >> > + int >> > + default 1000 # Ethernet wants good queues >> > + help >> > + Set the default value of tx_queue_len for newly created network >> > + interfaces. It is used by queueing disciplines to determine how many >> > + packets to keep in backlog before starting to drop new ones. >> > + >> > + The default value of 1000 packets is there for a very long time and >> > + in combination with GSO way too big. >> > + >> >> I can't see how this could be used in a meaningful way. >> >> No distro is going to touch this. >> >> I don't think sysctl value would help either. > > I just didn't want to introduce yet another magic value assignment. It's > merely a #define with a little flexibility and a subtle note that the > default should be changed attached. Like others have mentioned, fix the _REAL_ issue. Which is that there are devices (virtual or whatever) which don't want a qdisc attached no matter what. Flag those devices as such and adjust the qdisc attachment logic to check that new flag. Anything is better than hacking the queue len.