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Old 19th January 2009
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TerryP TerryP is offline
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Join Date: May 2008
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Ok, here is an example:

Windows XP requires a minimal of 64MB of RAM; 128MB is recommended (although how anyone could live with that on XP, is beyond me). So let us say, QEMU will be allowed 96MB of memory for running an Windows XP image. Let us further postulate, that between stumpwm and QEMU itself, a further 4MB of memory is consumed (fair enough? This will probably be a bit worse, depending on the size of the disk image used with QEMU).

This leaves 156MB of memory free, not deducting memory space used by the Kernel, hardware resources, or incurred by file system related operations (a background fsck perhaps?).

You will have to be running the X Windows System. A standard X.Org installation I believe, maps part or all of the gfx cards memory into it's own address space where possible; so memory usage on X.Org should be less then most things could ever report; I'm not familiar with NetBSDs X setup, but assume it would be similiar to normal X.Org/Xenocara. So, let us say at least 20MB of system memory for X. If your graphics card uses shared memory, like several (cheaper) ATI Xpress and Intel GMA cards do; that will increase the drain on system memory. X also should be caching image data used by programs, so that out to keep its memory usage lower....

So in reality, you've got closer to < 2/3 your memory to run other applications in. The exact memory used by programs is very hard to gauge, and the figures I've given are for the sake of *example* only. Needless to say, running things like OpenOffice, MS Office, Flash player, Mozilla, running a 3D game, encoding/decoding video, or building anything from ports or with GCC -- will further reduce your memory closer to swap space by a 'nice chunk'. In short: it helps drains system resources, which depending on your needs could someday become a problem sooner then later. FreeBSD is pretty efficient with it's usage of memory IMHO, but not always wise to push it to low memory situations. That is why I said, 'If you only have 256MB for both NetBSD/X, adding QEMU is probably not a great idea.' If one wants to run multiple OSes at once.... oy: much higher chance of getting into SWAP.

Running Windows in QEMU with 96MB of RAM available to it, plus MS Office and IE6; alone would probably push XP into using SWAP file on the disk image. Most Linux or BSD systems, you'd want at least 64MB for QEMU... but ya get my point.

You should really test it out before you commit to it, if you have a real need for using it in such a configuration; rather then a passing fancy.

--> That is my 2 cents.
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