netdev - Re: RCU problems in fib_table

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Date:	Tue, 6 Apr 2010 23:45:03 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Robert Olsson <robert@...julf.net>
Cc:	Andi Kleen <andi@...stfloor.org>, robert.olsson@....uu.se,
	netdev@...r.kernel.org, Jens.Laas@....uu.se
Subject: Re: RCU problems in fib_table_insert

On Wed, Apr 07, 2010 at 08:10:13AM +0200, Robert Olsson wrote:
> 
> Paul E. McKenney writes:
>  > On Mon, Mar 22, 2010 at 07:18:34AM +0100, Robert Olsson wrote:
>  > > 
>  > > Seems like Paul and Eric fixed this problem... We use fib_trie with 
>  > > major infrastructure but always disable preempt. It was unsafe w.
>  > > preempt at least before Jareks P. patches about a year ago. I havn't
>  > > tested w. preempt after that but maybe someone else have...
> 
> 
>  > Though I must admit that I would be surprised if there wasn't
>  > more adjustment required in net/ipv4/fib_trie.c -- lots of
>  > rcu_dereference()s in there.
> 
>  Hi, a follow on this thread. 
> 
>  Maybe I was to pessimistic... we've setup  for stress test running during 
>  easter vacation
> 
>  Testing the fib_trie with preempt enabled. Continuesly loading/flushing  
>  "full BGP" via a test script, while routing without the route cache 
>  to further stress locking. Average load about 300 kpps. Some more test 
>  details below.
> 
>  The test was manually stopped after 6 days. So it seems like preempt/rcu 
>  has been improved with fib_trie.

Always happy to be pleasantly surprised.  ;-)

							Thanx, Paul

>  Thanks
> 					--ro
> 
> HW
> --
> CPU  Opteron 2 * 6174, TYAN S8230. Intel 82599
> 
> Kernel from net-next-2.6
> ------------------------
> Version 2.6.34-rc1bifrost-x86_64 (gcc version 4.3.2 (GCC) ) #4 SMP PREEMPT
> CONFIG_PREEMPT=y
> CONFIG_DEBUG_PREEMPT=y
> CONFIG_IP_FIB_TRIE=y
> CONFIG_FIB_RULES=y
> CONFIG_TREE_RCU=y
> CONFIG_RCU_FANOUT=64
> 
> IP table
> --------
> "BGP" 279 k routes
> 
> Test duration
> -------------
> 09:34:14 up 6 days, 20:57,  4 users,  load average: 5.28, 5.87, 5.53
> 
> Test script
> -----------
> #! /bin/bash
> while(true) do
>   ip -batch /etc/inet_route_add.bat; 
>   ip route list | wc -l;  ( 279 k routes )
>   ifconfig eth1 down 
>   ifconfig eth1 10.10.11.1 netmask 255.255.255.0
>   ip route list | wc -l;  ( 3 routes )
> done;
> 
> /proc/net/softnet_stat
> 
> 0000d503 00000000 00000014 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 4cc1ecfb 00000000 02bb1bcb 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 4cb95da1 00000000 02cc6574 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 4cb17932 00000000 02e1abdf 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 4cc40ad9 00000000 02f53db0 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 4cbfe34f 00000000 0306a88d 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 4ccb10e9 00000000 03d3a11d 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 4ca84c29 00000000 03be0ca1 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 4cb710f8 00000000 04070289 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 0b505d55 00000000 038a9bc0 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 0b54a7be 00000000 03a5de6d 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 0b5be81f 00000000 03be018c 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 0b51fdd0 00000000 0559fdd6 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 0b4fa6fd 00000000 056311dc 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 0b4a61d3 00000000 056a9276 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 0b454970 00000000 0572add1 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> 
> FYI. CPU0 is resvered for BGP/ssh/stats etc
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