Glance Plus & Memory

[Jason Nickelson_1]

We've got a K580 running HP-UX 11.0 32-bit with 4GB of memory. If I use any tool other than Glance Plus, I see all 4GB. But in Glance it only shows 3.75GB physical memory. Is there a patch I missed? I'm running version C.03.05.00. I realize it's not that big of a deal, but I use screenshots of the nice pretty graphs for management to look at. It's kind of embarassing when I tell them there is 4GB, but they keep seeing paperwork that says otherwise.

[Sandip Ghosh]

It is like that because 32bit Kernel can't address 4 GB of memory. It can acces upto 3.75 GB of Memory.That is the limitation of 32 bit Kernel.

Sandip

[Helen French]

Hi Jason,

I think the reason is the 32bit OS. 10.x and 11.X 32 bit versions of OS only allow a maximum addressable memory of 3.75GB. I am not sure about a patch for this, but try loading the latest patch bundle.

Also K580 will support 64bit OS, so I would suggest you to install 64bit OS on your server.

HTH,
Shiju

[Jason Nickelson_1]

Thanks for the quick responses. I would love to go to 64bit, but because of internal politics we can't, I won't go into it. I could have sworn that the 32bit OS limit was 4GB ... well, 32 x 1's = ffffffff = 4GB - 1. Is it because of the -1? Where is the waste coming from in the kernel? I suppose it wouldn't make a difference if I pulled out 256MB and used it in another system then? Just seems like a waste.

[Helen French · Accepted solution]

Hi Jason:

Again, it is not a waste and DONT remove it. The calculation is like this:

2^32 = 4 GB addressable memory - 256 MB reserved for I/O address space

The 256MB is used by the I/O.

HTH,
Shiju

[Jason Nickelson_1]

Ah, I see. The system actually uses all 4GB, but not all of it is user memory. I studied operating systems in college, but it wasn't as in depth as I would have liked. Thanks for the clarification.

[Bill Hassell]

The most important documents about 32bit programs is found in /usr/share/doc. The details are fairly unique to HP-UX and point out the severe limitations of 32bit programs. There is nothing you can do about these limits...they have always existed.

A 64bit kernel will not change these limits for 32bit programs. Programs must be recoded and/or recompiled to be 64bit executables to use dozens of gigabytes of RAM.

There is a workaround for 32bit shared memory (which is limited to one quadrant or less than 1000 megs or 1750 megs with 'MAGIC') called memory windows. If you don't recent patches, you'll have to read the details at docs.hp.com.