From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH 4/9] AF_UNIX: find the recipients for multicast messages Date: Mon, 22 Nov 2010 11:05:19 -0800 (PST) Message-ID: <20101122.110519.39205345.davem@davemloft.net> References: <20101122183447.124afce5@chocolatine.cbg.collabora.co.uk> <1290450982-17480-4-git-send-email-alban.crequy@collabora.co.uk> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: eric.dumazet@gmail.com, shemminger@vyatta.com, gorcunov@openvz.org, adobriyan@gmail.com, lennart@poettering.net, kay.sievers@vrfy.org, ian.molton@collabora.co.uk, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: alban.crequy@collabora.co.uk Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:38191 "EHLO sunset.davemloft.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750793Ab0KVTEy (ORCPT ); Mon, 22 Nov 2010 14:04:54 -0500 In-Reply-To: <1290450982-17480-4-git-send-email-alban.crequy@collabora.co.uk> Sender: netdev-owner@vger.kernel.org List-ID: From: Alban Crequy Date: Mon, 22 Nov 2010 18:36:17 +0000 > unix_find_multicast_recipients() builds an array of recipients. It can either > find the peers of a specific multicast address, or find all the peers of all > multicast group the sender is part of. > > Signed-off-by: Alban Crequy You really should use RCU to lock this stuff, this way sends run lockless and have less worries wrt. the memory allocation. You'll also only take a spinlock in the write paths which change the multicast groups, which ought to be rare. Although to be honest you should optimize the case of small numbers of recipients, in the same way we optimize small numbers of iovecs on sends. Have an on-stack array that holds a small number of entries and use that if the set fits, otherwise dynamic allocation.