Subject: Re: kernel 2.6.25-rc7 highly unstable on high load

From: Eric Dumazet <[email-masked]>
Date: Thu, 27 Mar 2008 15:52:19 +0100

Denys Fedoryshchenko a écrit :
> Yes, it seems related to routing. Before such thing was not happening (maybe 
> because TRIE was operating better?).
>
> Here is info at "peak time", i disable nmi_watchdog now, so garbage collector 
> will not be triggered by nmi watchdog. 
>
> 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|
>   247011| 2255410|  162866|       0|     610|       5|       0|       0|   
> 33761|    8574|       0|  165475|  165307|       0|       0|10407428|  174948|
>   251810|   43087|    2782|       0|       9|       0|       0|       0|     
> 618|     122|       0|    2912|    2909|       0|       0|  241946|    3796|
>   256277|   43035|    2739|       0|       9|       0|       0|       0|     
> 595|     121|       0|    2867|    2864|       0|       0|  243724|    3748|
>   260177|   43596|    2647|       0|       8|       0|       0|       0|     
> 672|     123|       0|    2778|    2776|       0|       0|  246880|    4048|
>   232741|   42270|    2759|       0|      15|       0|       0|       0|     
> 665|     135|       0|    2910|    2907|       0|       0|  233990|    3938|
>   226623|   42615|    2792|       0|      11|       0|       0|       0|     
> 723|     132|       0|    2935|    2932|       0|       0|  218378|    3862|
>   233190|   42397|    2778|       0|       8|       0|       0|       0|     
> 675|     128|       0|    2913|    2909|       0|       0|  214258|    3703|
>   239093|   42342|    2713|       0|       9|       0|       0|       0|     
> 764|     126|       0|    2847|    2845|       0|       0|  216453|    4080|
>   150539|   36992|    7564|       0|      58|       0|       0|       0|     
> 539|     283|       0|    7902|    7900|       0|       0|   93459|    1996|
>   154441|   40258|    4422|       0|      12|       0|       0|       0|     
> 655|     212|       0|    4644|    4640|       0|       0|   77271|    1458|
>
> On one "crash" i got 
> Mar 27 11:27:15 205.177.186.74 [ 7141.156100] dst cache overflow
> Mar 27 11:27:15 205.177.186.74 [ 7141.002291] dst cache overflow
> Mar 27 11:27:15 205.177.186.74 [ 7141.162756] dst cache overflow
>
> So i increase now routes amount more than 512K to 5120K, and will see more.
>   
You want to tune route cache for your special needs, and not permit it 
to store 5 millions entries !

# default is a gc every 60 seconds, not good for large caches
echo 1 >/proc/sys/net/ipv4/route/gc_interval
# default is 8 entries per slot..
echo 4 >/proc/sys/net/ipv4/route/gc_elasticity
# avoid a flush every 10 minutes
echo 3600 >/proc/sys/net/ipv4/route/secret_interval

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