From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH 4/5 (resend)] net: Make ifindex generation per-net namespace (v2) Date: Tue, 07 Aug 2012 15:13:12 +0200 Message-ID: <1344345192.28967.88.camel@edumazet-glaptop> References: <501FD0F2.4040609@parallels.com> <501FD15F.70604@parallels.com> <5020F5C3.8010107@parallels.com> <1344341466.28967.78.camel@edumazet-glaptop> <50210C23.2070203@parallels.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: David Miller , "Eric W. Biederman" , Linux Netdev List To: Pavel Emelyanov Return-path: Received: from mail-bk0-f46.google.com ([209.85.214.46]:64796 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754638Ab2HGNNS (ORCPT ); Tue, 7 Aug 2012 09:13:18 -0400 Received: by bkwj10 with SMTP id j10so1439324bkw.19 for ; Tue, 07 Aug 2012 06:13:17 -0700 (PDT) In-Reply-To: <50210C23.2070203@parallels.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 2012-08-07 at 16:37 +0400, Pavel Emelyanov wrote: > >> @@ -62,6 +62,7 @@ struct net { > >> struct sock *rtnl; /* rtnetlink socket */ > >> struct sock *genl_sock; > >> > >> + int ifindex; > > > > could you place ifindex right after dev_base_seq : avoid two holes > > and use the same cache line, dirtied in > > list_netdevice()/unlist_netdevice() > > Sure! Here it is: > > From: Pavel Emelyanov > Subject: [PATCH 4/5] net: Make ifindex generation per-net namespace > > Strictly speaking this is only _really_ required for checkpoint-restore to > make loopback device always have the same index. > > This change appears to be safe wrt "ifindex should be unique per-system" > concept, as all the ifindex usage is either already made per net namespace > of is explicitly limited with init_net only. > > There are two cool side effects of this. The first one -- ifindices of > devices in container are always small, regardless of how many containers > we've started (and re-started) so far. The second one is -- we can speed > up the loopback ifidex access as shown in the next patch. > > v2: Place ifindex right after dev_base_seq : avoid two holes and use the > same cache line, dirtied in list_netdevice()/unlist_netdevice() > > Signed-off-by: Pavel Emelyanov > --- Acked-by: Eric Dumazet