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Kernel Parameter mafiles_lim showing more than 400%

 
Kamaleshan
Occasional Advisor

Kernel Parameter mafiles_lim showing more than 400%

Hi ,

 

In our DB server kcusage for maxfiles_lim always showing more than 400% . 

Server Model - rx6600 , OS- 11.31

 

We are having 2 servers which is configured in RCA Oracle clustering. We set both servers kernel parameters are same, (maxfiles_lim = 4096)  But in one server maxfiles_lim always showing more than 400% , in another its showing less than 40%. I am not getting any performance issue on servers. 

 

My Questions:

 

1. What is use of maxfiles_lim ?

2. How kernel allows to use more than configured settings for maxfiles_lim ?

3. What is the resolution?

 

Regards,

Kamaleshan

 

12 REPLIES 12
Dennis Handly
Acclaimed Contributor

Re: Kernel parameter maxfiles_lim showing more than 400%

>1. What is use of maxfiles_lim?

 

Limit run away processes from opening too many files.

 

>2. How kernel allows to use more than configured settings for maxfiles_lim?

 

Possibly root processes can bypass the limit?

Kamaleshan
Occasional Advisor

Re: Kernel parameter maxfiles_lim showing more than 400%

>1. What is use of maxfiles_lim?

 

> Limit run away processes from opening too many files.

 

See I have two servers both are configured in RCA Clustering with Load balancing  , So why only one server is showing high utilization of  maxfiles_lim  ? Why not another server?

 

 

Regards,

Kamaleshan 

Dennis Handly
Acclaimed Contributor

Re: Kernel parameter maxfiles_lim showing more than 400%

>So why only one server is showing high utilization of  maxfiles_lim?

 

Are both configured the same are they running the same programs?  What is the max usage number instead of the percentage?

Kamaleshan
Occasional Advisor

Re: Kernel parameter maxfiles_lim showing more than 400%

> Are both configured the same are they running the same programs? 

Yes , Oracle 10G is configured & Running on Both Servers with RCA Clustering.

 

 > What is the max usage number instead of the percentage?

 

Tunable            Usage / Setting
======================
maxfiles_lim   49873 / 4096

 

usage is - 49873

 

Regards,

Dennis Handly
Acclaimed Contributor

Re: Kernel parameter maxfiles_lim showing more than 400%

>usage is - 49873

 

On both?

Kamaleshan
Occasional Advisor

Re: Kernel parameter maxfiles_lim showing more than 400%

Server 1 Usage is -  49873

 

Server 2 Usage is - 1366 

 

Setting is 4096 for both servers,

 

 

Regards,

 

Dennis Handly
Acclaimed Contributor

Re: Kernel parameter maxfiles_lim showing more than 400%

>Server 1 Usage is -  49873 Server 2 Usage is - 1366

 

Looks like Server 1 is different, busier or running different applications.

I'm not sure this is worth worrying about.

Kamaleshan
Occasional Advisor

Re: Kernel parameter maxfiles_lim showing more than 400%

Both the servers are running same applications & I checked Server utilization that is also almost same. 

Already informed to my database team they also checking with their end. 

 

Thanks for your replay . If I ll get any update from my team , I ll post.

 

 

Regards,

 

Santosh Abraham
Advisor

Re: Kernel parameter maxfiles_lim showing more than 400%

One possibility is that maxfiles_lim may have been configured to a higher value previously (maybe 64k), and the files opened by a process could have grown  to that value.  This value is cached in a per-process data structure and the process can open files upto that value.

 

Later on when you changed the maxfiles_lim to a lower value, i.e 4096 it will not apply to processes created prior to the new changed value.

 

kcusage -t maxfiles_lim can be used to determine which are the top 5 processes and their pids, consuming files.

kclog -n maxfiles_lim will tell when the tunable change was applied.

 

Maybe you can co-relate the two to find out when the process was created.  If it was created prior to the tunable change you have your answer.