[Mongrel] performance observation on redhat

barsalou barjunk at attglobal.net
Sun Sep 23 14:41:35 EDT 2007


Armin,

Since your goofing around with that, how about some of the other 
settings like maxtime and ttl values?

Seems like you have deleayd when some garbage collection operations are 
taking place, so maybe tweeking that a little more will give you the 
performance your looking for.

I've never used this feature, but thought that might interesting as well.

Mike B.

Quoting "Wayne E. Seguin" <wayneeseguin at gmail.com>:

> On Sep 23, 2007, at 02:30 , armin roehrl wrote:
>> Hi,
>>
>>     I made an interesting observation using webservers (not just  
>> mongrel) under red hat enterprise
>> linux ES release 4 (Nahant Update 5). Maybe this is helpful or  
>> somebody with deeper networking
>> expertise can comment on this.
>>
>> Once client said that 1-2% of the response of our server were  
>> unacceptably slow (really huge 3s-21s).
>> So I did more  ab and httperf tests and notice that very few  
>> requests do take a very long time. Being clueless
>> I first thought that the ruby garbage collector or mongrel is  
>> causing the effect, so after looking
>> at a similar setup using erlang's yaws or nginx alone, I noticed  
>> that sometimes this can happen,
>> especially when increasing the number of concurrent connects to a  
>> large number (e.g. 250-500).
>> I did the same on OS-X and did not notice these outliers.
>>
>> After a lot of painful searching by luck we found one cure:  
>> inet_peer_threshold was too small.
>> Chaging it to a much larger value made the problem go away.
>>
>> echo 500000 > /proc/sys/net/ipv4/inet_peer_threshold
>>
>> There is a trade-off here. A too small value causes too many delays  
>> from inet-peer-storage cleaning
>> and a too big value makes life well for some limited time, but when  
>> it hits you, it becomes really expensive.
>>
>> Did you ever see this?
>>
>> Thanks,
>>   -Armin
>
> Armin,
>
> We might put this in the documentation, will discuss with the dev team.
>
> Thank you for this.
>
>   ~Wayne
>
> s///g
> Wayne E. Seguin
> Sr. Systems Architect & Systems Administrator
>
>



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