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Message-ID: <4B96A24A.6060405@utah.edu> Date: Tue, 09 Mar 2010 12:32:26 -0700 From: Tom Ammon <tom.ammon@...h.edu> To: linux-kernel@...r.kernel.org Subject: how to tweak ARP timer on kernel 2.6.9 Hi, I've been trying to figure out how to adjust the ARP timeout on kernel 2.6.9 and I found the following in /proc/sys/net/ipv4/neigh/ib0 (its an IB interface I am interested in changing) with the following values. This is on kernel 2.6.9-89ELsmp (RHEL4) : [root@...55 ib0]# cat anycast_delay 99 [root@...55 ib0]# cat app_solicit 0 [root@...55 ib0]# cat base_reachable_time 30 [root@...55 ib0]# cat delay_first_probe_time 5 [root@...55 ib0]# cat gc_stale_time 60 [root@...55 ib0]# cat locktime 99 [root@...55 ib0]# cat mcast_solicit 3 [root@...55 ib0]# cat proxy_delay 79 [root@...55 ib0]# cat proxy_qlen 64 [root@...55 ib0]# cat retrans_time 99 [root@...55 ib0]# cat ucast_solicit 3 [root@...55 ib0]# cat unres_qlen 3 When I test this, along with per-flow ECMP (using the iproute2 utils), I see that the ARP cache is timing out about every 10 minutes (I observe this by load balancing an iperf flow between two different gateway machines and then graphing the interface traffic) On a newer kernel, 2.6.18-164.11.1.el5 (RHEL5), I see mostly the same parms available, but a few new ones have been added. However, all of the parms that are the same name between the two kernels are the same values: [root@...eway2 ib0]# cat anycast_delay 99 [root@...eway2 ib0]# cat app_solicit 0 [root@...eway2 ib0]# cat base_reachable_time 30 [root@...eway2 ib0]# cat base_reachable_time_ms 30000 [root@...eway2 ib0]# cat delay_first_probe_time 5 [root@...eway2 ib0]# cat gc_stale_time 60 [root@...eway2 ib0]# cat locktime 99 [root@...eway2 ib0]# cat mcast_solicit 3 [root@...eway2 ib0]# cat proxy_delay 79 [root@...eway2 ib0]# cat proxy_qlen 64 [root@...eway2 ib0]# cat retrans_time 99 [root@...eway2 ib0]# cat retrans_time_ms 1000 [root@...eway2 ib0]# cat ucast_solicit 3 [root@...eway2 ib0]# cat unres_qlen 3 Yet when I observe the same traffic flow with this machine, the ARP cache times out about once per minute. Is there another set of parameters somewhere that govern how often the kernel times out the ARP cache? If so, where might I find that? Is there any kernel documentation that talks about changing ARP timers on the linux kernel? Tom Ammon -- -------------------------------------------------------------------- Tom Ammon Network Engineer Office: 801.587.0976 Mobile: 801.674.9273 Center for High Performance Computing University of Utah http://www.chpc.utah.edu -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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