Re: Kernel panic: Route cache, RCU, possibly FIB trie.

[Eric Dumazet <dada1@cosmosbay.com>]

Jesper Dangaard Brouer a écrit :
> On Thu, 23 Mar 2006, Eric Dumazet wrote:
>
> > Jesper Dangaard Brouer a écrit :
> >
> > > > grep . /proc/sys/net/ipv4/route/*
> > > > /proc/sys/net/ipv4/route/error_burst:5000
> > > > /proc/sys/net/ipv4/route/error_cost:1000
> > > > grep: /proc/sys/net/ipv4/route/flush: Operation not permitted
> > > > /proc/sys/net/ipv4/route/gc_elasticity:8
> > > > /proc/sys/net/ipv4/route/gc_interval:60
> > > > /proc/sys/net/ipv4/route/gc_min_interval:0
> > > > /proc/sys/net/ipv4/route/gc_min_interval_ms:500
> > > > /proc/sys/net/ipv4/route/gc_thresh:65536
> > > > /proc/sys/net/ipv4/route/gc_timeout:300
> > > > /proc/sys/net/ipv4/route/max_delay:10
> > > > /proc/sys/net/ipv4/route/max_size:1048576
> > > > /proc/sys/net/ipv4/route/min_adv_mss:256
> > > > /proc/sys/net/ipv4/route/min_delay:2
> > > > /proc/sys/net/ipv4/route/min_pmtu:552
> > > > /proc/sys/net/ipv4/route/mtu_expires:600
> > > > /proc/sys/net/ipv4/route/redirect_load:20
> > > > /proc/sys/net/ipv4/route/redirect_number:9
> > > > /proc/sys/net/ipv4/route/redirect_silence:20480
> > > > /proc/sys/net/ipv4/route/secret_interval:600
> > I would say : Change the settings :)
> >
> > echo 2 > /proc/sys/net/ipv4/route/gc_elasticity
> > echo 1 > /proc/sys/net/ipv4/route/gc_interval
> > echo 131072 > /proc/sys/net/ipv4/route/gc_thresh
> These parameters do not solve the problem. I think you missed my 
> previous point.  The parameter that needs adjustment is:
>  /proc/sys/net/ipv4/route/max_size
>
> The garbage collector will not be activated before the number of entries 
> are above "max_size" (see: function rt_garbage_collect).
> I have set:
>  /proc/sys/net/ipv4/route/gc_thresh:30000
>  /proc/sys/net/ipv4/route/max_size:30000
>
> Which solves the problem of the route cache growing too large too fast.
>
>
> I have read the route.c code again, to see if I missed something. Are 
> you trying to make the function "rt_check_expire" to do the cleanup?
> I have tried your parameters, and it does not have the desired effect.
I was just guessing, since you didnt give us your rtstat output.

If you start to hit max_size then you have really a problem.

And no, I was not trying to make the garbage collector starts. This cost way 
too much cpu, the router drops packets.
On my routers, I try to size the rt hash table appropriatly (boot param : 
rhash_entries=1048575 for example), and keep the chains small, to avoid 
spending too much cpu time (and too much memory cache lines touched) in 
{soft}irq processing.
But yes it uses some memory.

# rtstat -c10 -i1
rt_cache|rt_cache|rt_cache|rt_cache|rt_cache|rt_cache|rt_cache|rt_cache|rt_cache|rt_cache|rt_cache|rt_cache|rt_cache|rt_cache|rt_cache|rt_cache|rt_cache|
 entries|  in_hit|in_slow_|in_slow_|in_no_ro|  in_brd|in_marti|in_marti| 
out_hit|out_slow|out_slow|gc_total|gc_ignor|gc_goal_|gc_dst_o|in_hlist|out_hlis|
        |        |     tot|      mc|     ute|        |  an_dst|  an_src| 
   |    _tot|     _mc|        |      ed|    miss| verflow| _search|t_search|
 1672276|   32062|    4688|       0|       0|       0|       0|       0| 
2124|    2176|       0|       0|       0|       0|       0|   26020|    4385|
 1671142|   31826|    4626|       0|       0|       0|       0|       0| 
2055|    1906|       0|       0|       0|       0|       0|   25617|    4124|
 1670424|   31473|    4702|       0|       0|       0|       0|       0| 
2221|    2144|       0|       0|       0|       0|       0|   25348|    4340|
 1670928|   31671|    7600|       0|       0|       0|       0|       0| 
2037|    2152|       0|       0|       0|       0|       0|   30354|    4245|
 1670444|   31704|    4818|       0|       0|       0|       0|       0| 
2037|    1927|       0|       0|       0|       0|       0|   25424|    3871|
 1670133|   31785|    4598|       0|       0|       0|       0|       0| 
1988|    2184|       0|       0|       0|       0|       0|   24946|    4302|
 1669990|   31544|    4700|       0|       0|       0|       0|       0| 
2022|    2188|       0|       0|       0|       0|       0|   25092|    4357|
 1669880|   31930|    4750|       0|       0|       0|       0|       0| 
2054|    2002|       0|       0|       0|       0|       0|   25703|    4214|

Eric
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