Kernel parameter bufpages

[Marc Bohnert]

I am running on a N class machine 4 GB memory HPUX 11.0.

What is the tuneable parameter bufpages used for?

The parameter bufpages is statically configured for a size of 2648. Should this parameter be set to 0 and allow the kernel to dynamcally allocated needed space.

I am receiving ENOBUF from an accept system call and thought that this parameter may be the contributing factor.

Is there a way to find out in real time what high water mark this parameter has reached?


Thank you in advance,

Marc Bohnert

[A. Clay Stephenson]

This is the number of 4k pages allocated for file buffers. It is almost certainly way too small. You have two choices; set it to 0 and let the system do dynamic buffer cacheing or
set it to a value ~10% of total RAM. If you use dynamic make sure that dbc_max_pct is no more than about 25% and ~15% is better. min_dbc_pct should be ~5%. If you use bufpages <> 0 then I would set nbuf to 0.

[Lasse Knudsen]

As written it is 4 kb buffers used for file caching. I think the recommended way is to set it to '0' and use dbc_max&min_pct to control the file cache. Depending on what the server is used for you would apply different values.

If you use NFS-filesystem on this machine your buffer cache should not exceed 300MB. In your case that would give a dbc_max_pct of 8-9.

If you need a static configured cache size just set dbc_max_pct and dbc_min_pct to the same number.

And ENOBUF has got nothing to do with this - read:

http://forums.itrc.hp.com/cm/QuestionAnswer/1,1150,0x23677e990647d4118fee0090279cd0f9,00.html

/Allan

[James R. Ferguson]

Hi Marc:

In addition to the contributions of Clay & Allan above (and the links cited by Allan), take a look at the kernel configuration documentation here:

http://docs.hp.com/hpux/onlinedocs/os/11i/kcparams/KCparams.OverviewAll.html

This, and earlier versions, note that 'nbuf' is for backwards compatibility and should be set to zero because dynamic buffer cache is preferred. Dynamic buffer cache is mangaged by 'dbc_max_pct' and 'dbc_min_pct'.

The current amount of memory used for this buffer cache can be seen with 'glance'.

...JRF...