From mboxrd@z Thu Jan 1 00:00:00 1970 From: roopa Subject: Re: [PATCH net-next RFC] rtnetlink: add new RTM_GETSTATS to dump link stats Date: Wed, 24 Feb 2016 21:25:50 -0800 Message-ID: <56CE905E.4030601@cumulusnetworks.com> References: <1456207293-36903-1-git-send-email-roopa@cumulusnetworks.com> <20160224.164003.357595978348193472.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, jhs@mojatatu.com To: David Miller Return-path: Received: from mail-pf0-f175.google.com ([209.85.192.175]:35546 "EHLO mail-pf0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750739AbcBYFZx (ORCPT ); Thu, 25 Feb 2016 00:25:53 -0500 Received: by mail-pf0-f175.google.com with SMTP id c10so27219658pfc.2 for ; Wed, 24 Feb 2016 21:25:52 -0800 (PST) In-Reply-To: <20160224.164003.357595978348193472.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On 2/24/16, 1:40 PM, David Miller wrote: > From: Roopa Prabhu > Date: Mon, 22 Feb 2016 22:01:33 -0800 > >> From: Roopa Prabhu >> >> This patch adds a new RTM_GETSTATS message to query link stats via netlink >> from the kernel. RTM_NEWLINK also dumps stats today, but RTM_NEWLINK returns a >> lot more than just stats and is expensive in some cases when frequent >> polling for stats from userspace is a common operation. > Even worse, we push two copies of the same exact stats. Once to give > the (deprecated) 32-bit rtnl stats, and once to give the 64-bit ones. > > This is rather rediculous, but was probably done for compatability. i would think so. > >> To begin with, this patch adds the following types of stats (which are >> also available via RTM_NEWLINK today): >> >> struct nla_policy ifla_stats_policy[IFLA_LINK_STATS_MAX + 1] = { >> [IFLA_LINK_STATS] = { .len = sizeof(struct rtnl_link_stats) }, >> [IFLA_LINK_STATS64] = { .len = sizeof(struct rtnl_link_stats64) }, >> [IFLA_LINK_INET6_STATS] = {. type = NLA_NESTED }, >> }; > I think we should skip the old 32-bit stats and only provide the full > native 64-bit rtnl_link_stats64. Apps have to have changes to use > this new facility, therefore they can be adjusted for the (extremely > minimal) amount of work necessary to understand 64-bit stats if > necessary. > > By using rtnl_fill_stats() we would unnecessarily continue to send > duplicate and extra information unnecessarily. > > We have the chance to fix this here, so let's take advantage of the > opportunity to promote the data structure which can then be a first > class citizen not only in the kernel but in userspace too. agree, very much > >> Filtering stats (if the user wanted to query just ipv6 stats ?): >> a) I have a version of the patch that uses 'struct ifinfomsg->ifi_family' >> as a filter from userspace. But, given that in the future we may want to >> not just filter by family, I have dropped it in favor of >> attribute filtering (not included in this patch but point b) below). >> >> b) RTM_GETSTATS message to contain attributes in the request message >> >> nlmsg_parse(nlh, ....IFLA_LINK_STATS_MAX, ifla_stats_policy...) >> >> if tb[IFLA_LINK_INET6_STATS] >> include ipv6 stats in the dump >> >> if tb[IFLA_LINK_MPLS_STATS] >> include mpls stats in the dump > I wonder if an additive method is better. Provide IFLA_LINK_STATS64 > by default, and the user has to ask for more. > > Or the user gets nothing, and a simply u32 bitmap in the request acts > as a selector, with enable bits for each stat type. > > It really has to be easy to carve out exactly the information the user > wants, and be very minimal by default in order to be as efficient as > possible. ok, agreed here too. I like the default minimal approach. keeps it simple and efficient. I did go back and forth on the attribute vs mask. cosmetic but, i guess i did not feel good about having to redefine every attribute again for the bitmap filter ...and i anticipate the list of stat attributes to grow overtime (maybe there is a better way). enum { IFLA_LINK_STATS64, IFLA_LINK_INET6_STATS, IFLA_LINK_MPLS_STATS, __IFLA_LINK_STATS_MAX, }; #define IFLA_LINK_STATS64_FILTER 0 #define IFLA_LINK_INET6_STATS_FILTER (1 << 0) #define IFLA_LINK_MPLS_STATS_FILTER (2 << 0) Will post non-RFC with the changes later this week. Thanks for the feedback!.