From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH iproute2] man: Clarify idleslope calculation for tc-cbs Date: Sun, 12 Nov 2017 15:58:45 -0800 Message-ID: <20171112155845.69a079ae@xeon-e3> References: <20171110223436.18221-1-jesus.sanchez-palencia@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, jhs@mojatatu.com, xiyou.wangcong@gmail.com, jiri@resnulli.us, andre.guedes@intel.com, vinicius.gomes@intel.com, ivan.briano@intel.com To: Jesus Sanchez-Palencia Return-path: Received: from mail-pf0-f194.google.com ([209.85.192.194]:55935 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750985AbdKLX6u (ORCPT ); Sun, 12 Nov 2017 18:58:50 -0500 Received: by mail-pf0-f194.google.com with SMTP id 17so10592280pfn.12 for ; Sun, 12 Nov 2017 15:58:49 -0800 (PST) In-Reply-To: <20171110223436.18221-1-jesus.sanchez-palencia@intel.com> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 10 Nov 2017 14:34:36 -0800 Jesus Sanchez-Palencia wrote: > In order to calculate the idleSlope parameter of CBS correctly, users > must take into account the entire packet size, including the overhead > from all layers. > > Add some more details to the man page to clarify that, giving one > simple example and pointing users to the correct 802.1Q section for > further clarifications if needed. > > Signed-off-by: Jesus Sanchez-Palencia > --- > man/man8/tc-cbs.8 | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/man/man8/tc-cbs.8 b/man/man8/tc-cbs.8 > index 97e00c84..32e1e0d4 100644 > --- a/man/man8/tc-cbs.8 > +++ b/man/man8/tc-cbs.8 > @@ -43,7 +43,19 @@ second) when there is at least one packet waiting for transmission. > Packets are transmitted when the current value of credits is equal or > greater than zero. When there is no packet to be transmitted the > amount of credits is set to zero. This is the main tunable of the CBS > -algorithm. > +algorithm and represents the bandwidth that will be consumed. > +Note that when calculating idleslope, the entire packet size must be > +considered, including headers from all layers (i.e. MAC framing and any > +overhead from the physical layer), as described by IEEE 802.1Q-2014 > +section 34.4. > + > +As an example, for an ethernet frame carrying 284 bytes of payload, > +and with no VLAN tags, you must add 14 bytes for the Ethernet headers, > +4 bytes for the Frame check sequence (CRC), and 20 bytes for the L1 > +overhead: 12 bytes of interpacket gap, 7 bytes of preamble and 1 byte > +of start of frame delimiter. That results in 322 bytes for the total > +packet size, which is then used for calculating the idleslope. > + > .TP > sendslope > Sendslope is the rate of credits that is depleted (it should be a Applied to net-next