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32bit vs. 64bit for Virtual Machines

Last response: in Linux/Free BSD
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September 14, 2012 12:05:44 AM

I'm on a 64 bit OS and I'm running several Linux virtual machines. I'm wondering if there is any benefit to a 64 bit Linux distro over a 32 bit one. I know that a 64 bit OS allows over 4GB of RAM, but most of my VMs don't use that much. Is there any point to using a 64 bit distro over a 32 bit one for performance reasons? A 32 bit OS will (in theory) use less memory due to smaller pointers and instructions, so I'm a bit skeptical to switch to a 64 bit OS if I'm not going to use more than 4GB of RAM for the VM. Will instructions that use 64bits (int64 and doubles) process any faster?
a b 5 Linux
September 14, 2012 12:50:41 AM

certain functions run quicker under 64bit due to having larger pointers. x264 for example is ~%10 faster under 64bit. So really it depends on your software.
September 14, 2012 10:02:55 AM

Bear in mind what the future brings. Memory is pretty cheap these days, and often a good choice to improve performance (just threw out the original 2GB memory in a Macbook and placed 8GB inside - it does wonders).

If you have 64 bit Linux VMs you can later just copy them onto your new machine with more memory and be done. My old PC had a 32bit Linux installed and I never wanted to go through the trouble of a new install for using more memory, though I did have use for it. With regards to performance, I can't tell the difference between the two, but that's just because I never upgraded a 32bit machine to 64bit. I'll probably do that in the coming days with my old PC as I prepare it for my kids. If I see any noticeable difference, I'll post here.
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