[comp.sys.hp] HP kernel memory usage - how much and where?

dfh@bnrunix.UUCP (David F. Hinnant) (05/22/89)

When my HP-9000/360 (8 MB RAM, 19" B&W monitor) boots, it finds 8 MB of
real memory, and then tells me that about 6 MB is available as user
memory and a somewhat smaller number is lockable. Now the questions:

1) What is lockable memory (I presume this means that processes using
this memory can be locked in RAM.) and why is it different from user
memory?

2) My bare HP-UX kernel sizes at about 940K. What eats the remaining
~1.6 MB beside disk buffers? NFS cache? Is there anything that describes
which tunable parameters bump static tables and which tables are
allocated at boot time? I guess the video is memory mapped. How much
does this eat?

Thanks,


-- 

David Hinnant                    UUCP: ...{decvax,akgua}!mcnc!rti!bnrunix!dfh
Bell Northern Research           (919) 991-8299

stroyan@hpfcdc.HP.COM (Mike Stroyan) (05/23/89)

> When my HP-9000/360 (8 MB RAM, 19" B&W monitor) boots, it finds 8 MB of
> real memory, and then tells me that about 6 MB is available as user
> memory and a somewhat smaller number is lockable. Now the questions:
> 
> 1) What is lockable memory (I presume this means that processes using
> this memory can be locked in RAM.) and why is it different from user
> memory?

Lockable memory is a portion of available memory that can be used for
purposes other than normal VM paging.  Uses include process memory locked
by plock(2) and shared memory locked by shmctl(2) with SHM_LOCK.
The amount of memory designated lockable can be controlled by the
'unlockable_mem' configurable kernel parameter.

> 2) My bare HP-UX kernel sizes at about 940K. What eats the remaining
> ~1.6 MB beside disk buffers? NFS cache? Is there anything that describes
> which tunable parameters bump static tables and which tables are
> allocated at boot time? I guess the video is memory mapped. How much
> does this eat?
> 
> David Hinnant

The disk buffers are typically the largest part of the memory allocated.
By default are scaled in proportion to the amount of system memory
present.  Their size can be controlled by changing a kernel parameter
and rebuilding the kernel.  Appendix D of the "HP-UX System
Administrator Manual" describes several configurable kernel parameters
and the memory cost of each parameter.

The memory mapped graphics does not use system memory for the graphics
itself.  The frame buffer is specialized dual ported memory that is part
of the interface card and not reported as system memory.  There are a
few kilobytes of system memory used for the page tables to describe the
VM mapping of the frame buffer.

Mike Stroyan, stroyan@hpstryn