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Date: Mon, 27 Sep 2010 10:41:20 -0700 From: David Stevens <dlstevens@...ibm.com> To: David Miller <davem@...emloft.net> Cc: cl@...ux.com, linux-rdma@...r.kernel.org, netdev@...r.kernel.org, netdev-owner@...r.kernel.org, rda@...con.com Subject: Re: igmp: Allow mininum interval specification for igmp timers. David Miller <davem@...emloft.net> wrote on 09/23/2010 09:38:23 PM: > > > IGMP timers sometimes fire too rapidly due to randomization of the > > intervalsfrom 0 to max_delay in igmp_start_timer(). > ... > > Signed-off-by: Christoph Lameter <cl@...ux.com> > > > This change seems reasonable to me, what do you think David? [sorry for the delay -- I was off-line for the last few days] Dave, I don't know if you saw the more extended discussion we had on this or not, but I think while this would help for IB, it's not appropriate in general. These can in fact be "0" per RFC which is worst case for IB if there is a delay for being able to use the group, and the newer IGMPv3 standard has shortened the max interval from 10sec in v2 to 1 sec. Fundamentally, the problem is that the device needs to be able to send on the group immediately for IGMP; that it can't for IB is the problem, and I think it should be solved in IB by either queueing packets there or delaying there as needed before doing the joins. I don't think tweaking IGMP for this is appropriate at all, but if done there, it ought to be per-interface so it doesn't change anything for other network types which don't have this problem. It should be randomized and not the fixed delays to prevent storms on a mass start-up, and we also don't want to be increasing the number of duplicates for other network types. The default should be 2 reports in randomized 0-10 sec for each for v2, 2 in randomized 0-1 sec for v3. +-DLS -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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