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Date: Wed, 17 Nov 2010 05:43:37 +0100 From: Eric Dumazet <eric.dumazet@...il.com> To: Cypher Wu <cypher.w@...il.com> Cc: Chris Metcalf <cmetcalf@...era.com>, Américo Wang <xiyou.wangcong@...il.com>, linux-kernel@...r.kernel.org, netdev <netdev@...r.kernel.org> Subject: Re: Kernel rwlock design, Multicore and IGMP Le mercredi 17 novembre 2010 à 09:30 +0800, Cypher Wu a écrit : > O > struct in_device::mr_ifc_timer. Every time when a process join/leave a > MC group, igmp_ifc_event() -> igmp_ifc_start_timer() will start the > timer on the core that the system call issued, and > igmp_ifc_timer_expire() will be called on that core in the bottem halt > of timer interrupt. > If we call join/leave on mutlicores that timers will run on all these > cores, but it seems only one or two will generate IGMP message, others > will only lock the list and loop throught it with nothing generated. > > Problem would not be timer being restarted on different cores (very small impact), but scanning a list in igmpv3_send_cr() with many items in it and expensive things, under timer handler (softirq), so adding spikes of latency. IGMP_Unsolicited_Report_Interval is 10 seconds, so we start timer in a 5 second average. I am not sure there is a need to join/leave thousand of groups per second anyway... -- 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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