From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [net-next PATCH v1] net: netprio_cgroup: rework update socket logic Date: Sun, 22 Jul 2012 12:44:30 -0700 (PDT) Message-ID: <20120722.124430.1434387298248918593.davem@davemloft.net> References: <20120721020015.GA3827@neilslaptop.think-freely.org> <500AE08B.5040602@intel.com> <20120721171854.GA6099@neilslaptop.think-freely.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: john.r.fastabend@intel.com, netdev@vger.kernel.org, eric.dumazet@gmail.com, gaofeng@cn.fujitsu.com, lizefan@huawei.com To: nhorman@tuxdriver.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:38208 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752430Ab2GVTob (ORCPT ); Sun, 22 Jul 2012 15:44:31 -0400 In-Reply-To: <20120721171854.GA6099@neilslaptop.think-freely.org> Sender: netdev-owner@vger.kernel.org List-ID: From: Neil Horman Date: Sat, 21 Jul 2012 13:18:55 -0400 > On Sat, Jul 21, 2012 at 10:02:03AM -0700, John Fastabend wrote: >> On 7/20/2012 7:00 PM, Neil Horman wrote: >> >On Fri, Jul 20, 2012 at 01:39:25PM -0700, John Fastabend wrote: >> >>Instead of updating the sk_cgrp_prioidx struct field on every send >> >>this only updates the field when a task is moved via cgroup >> >>infrastructure. >> >> >> >>This allows sockets that may be used by a kernel worker thread >> >>to be managed. For example in the iscsi case today a user can >> >>put iscsid in a netprio cgroup and control traffic will be sent >> >>with the correct sk_cgrp_prioidx value set but as soon as data >> >>is sent the kernel worker thread isssues a send and sk_cgrp_prioidx >> >>is updated with the kernel worker threads value which is the >> >>default case. >> >> >> >>It seems more correct to only update the field when the user >> >>explicitly sets it via control group infrastructure. This allows >> >>the users to manage sockets that may be used with other threads. >> >> >> >>Signed-off-by: John Fastabend >> >I like the idea, but IIRC last time we tried this I think it caused problems >> >with processes that shared sockets. That is to say, if you have a parent and >> >child process that dup an socket descriptior, and put them in separate cgroups, >> >you get unpredictable results, as the socket gets assigned a priority based on >> >the last processed that moved cgroups. >> > >> >Neil >> > >> >> Shared sockets creates strange behavior as it exists today. If a dup >> of the socket fd is created the private data is still shared right. So >> in this case the sk_cgrp_prioidx value is going to get updated by both >> threads and then it is a race to see what it happens to be set to in >> the xmit path. >> >> With this patch at least the behavior is deterministic. Without it >> I can create the above scenario but have no way to determine what the >> skb priority will actually be set to. >> >> .John >> > Ok, I can buy that. Lets give this a try: > > Acked-by: Neil Horman > Applied.