[LARTC] Re: dst cache overflow

[Jesper Dangaard Brouer]

The values looks reasonable, garbage collection start (gc_thresh:32768) 
fairly early, but I often see that the GC cannot keep up.

The maximum size of the route cache max_size=524288 is okay, but it 
depends on the usage pattern.  On my production systems I has increased 
max_size to 2 million, to keep up!

Another interesting value is secret_interval:600, which is the interval 
the route cache is flushed, in seconds, that is 10 minuts.

  524288/600 = 873 packet/sec to new destinations.

You should realize that filling the route cache in 10 minuts can happen, 
as it only requires 873 packet/sec to new destinations.


What to do next:

Monitor the route cache, to see whats actually happening. The route cache 
counters are located in /proc/net/stat/rt_cache, but is not very human 
readable.  Use the tool "rtstat" to monitor the route cache.

The rtstat tool can be downloaded from Roberts site:
  ftp://robur.slu.se/pub/Linux/net-development/rt_cache_stat

Cheers,
   Jesper Brouer

--
-------------------------------------------------------------------
MSc. Master of Computer Science
Dept. of Computer Science, University of Copenhagen
Author of http://www.adsl-optimizer.dk
-------------------------------------------------------------------



On Wed, 10 Jan 2007, ArcosCom Linux User wrote:

> Here are:
>
> # 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: Operación no permitida
> /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:32768
> /proc/sys/net/ipv4/route/gc_timeout:300
> /proc/sys/net/ipv4/route/max_delay:10
> /proc/sys/net/ipv4/route/max_size:524288
> /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
>
>
> El Mie, 10 de Enero de 2007, 16:01, Jesper Dangaard Brouer escribió:
>>
>>
>> On Wed, 10 Jan 2007, ArcosCom Linux User wrote:
>>
>>> El Mie, 10 de Enero de 2007, 8:15, Patrick McHardy escribió:
>>>> ArcosCom Linux User wrote:
>>>>> The log says:
>>>>> Dec 30 00:52:27 cura kernel: dst cache overflow
>>
>> The log message "dst cache overflow" is normally related to overflow of
>> the route cache.  The max_size of the route cache can be adjusted through
>> /proc/sys/net/ipv4/route/max_size.
>>
>> What is your settings in /proc/sys/net/ipv4/route/?
>>
>> Run command:
>>   grep . /proc/sys/net/ipv4/route/*
>>
>> Hilsen
>>    Jesper Brouer
>>
>> --
>> -------------------------------------------------------------------
>> MSc. Master of Computer Science
>> Dept. of Computer Science, University of Copenhagen
>> Author of http://www.adsl-optimizer.dk
>> -------------------------------------------------------------------