Relationship of 'nfile' to Memory

[Michael Steele_2]

Hi:

The 'nfile' kernel parameter has been dynamic since I believe 11.00 and 64 bit CPU's. Not important. Somewhere around the intro of 11.00 the kernel parameter 'nfile' sent from static to dynamic and increased it's max value depending upon how much memory you had in your box.

I am looking for this relationship in some kind of formula or format like, for 1 GB max nfile is 1000. For 2 GB max nfile is 10,000.

Etc.

Does anyone have a citation or reference on this?

Thanks in Advance.!

[James R. Ferguson · Accepted solution]

Hi:

The manpages for 'nfile(5)' tell the story.

From the 11.23 manpages: "For small memory systems (less than 1GB), the default is 16384, or 16K. For systems with more than 1GB of memory, the default is 65536, or 64K...The minimum value allowed is 2048. The maximum value allowed is the maximum 32-bit signed integer value that can be represented in the system. The value is further constrained in that it must be equal to or greater than two times the per-process open file hard limit: (nfile >= 2*maxfiles_lim)."

At 11.31, the manpages note, "The default value for nfile is 0 (zero). The value of zero means that the system limit usually enforced by nfile will be disabled (that is, the number of system-wide open files is limited only by available memory)."

Regards!

...JRF...

[Dennis Handly]

On 11.31, this parm is obsolete since it is totally dynamic.

[Michael Steele_2]

Thanks. I've got an 11.23 box where 'nfile' continues to grow. Over 6 weeks there is steady growth with only 4 or 5 dips in total nfile during this 6 week time.

I am thinking:

a) open files are not been closed by the application and there may be a code issue.

And I'm looking for concurrence from the Forum or another reason for open files never being released back to the system.

Don't see anything else odd including no memory leaks.

Question: Will 'nfile' max out in 11.23?

[Patrick Wallek]

>>Question: Will 'nfile' max out in 11.23?

Yes, it definitely should.

What is the count of open files you see vs. your current nfile value? What does the 'file-sz' column look like in 'sar -v'?

[James R. Ferguson]

Hi (again) Michael:

> Question: Will 'nfile' max out in 11.23?

Yes, at the setting specified in your kernel. Dynamic means that you can change the parameter value immediately without a reboot.

Regards!

...JRF...

[Dennis Handly]

>a) open files are not been closed by the application and there may be a code issue.

Have you used glance or lsof to check to see what files are open for your suspect applications?

[Michael Steele_2]

Agreed.

But wouldn't you speculate that there is a code problem not closing open files?

[Dennis Handly]

>wouldn't you speculate that there is a code problem not closing open files?

Exactly, provided the number of processes is constant. (Files includes sockets, etc.)

[VK2COT]

Hello,

One additional word of caution:

Do not change nfile on HP-UX 11i v3!

Whilst it used to be very popular to change
it on older HP-UX releases, having non-zero
value on HP-UX 11i v3 can cause dramatical
problems, as few of our Oracle customers
experienced.

They preserved the values of nfile from HP-UX
11i v2 and the DB was having huge problems
and crashes.

Leave nfile on HP-UX 11i v3 as default.
It fact, it is now a PRIVATE KERNEL PARAMETER.

Cheers,

VK2COT

[Michael Steele_2]

VK2COT:

See Dennis' reply above and man page for 11.31 nfile. (* The default is 0 since nfile is dynamic in 11.31 *)