32bit vs 64bit Distro

[gerard4143]

Hi,

I had the opportunity to load Arch Linux/Gnome on a 32bit box and was surprised at the memory usage...With Gnome up and running and the system monitor open...I was getting a reading of 118MB. Now this is low especially when you consider on my Arch Linux/Gnome 64bit box I get a reading of 188Mb with Gnome running and the system monitor open...Why the discrepancy? The best I can figure:
1. Memory pointers are now 8 bytes instead of 4 bytes.
2. Memory alignment/padding may be out to 8 bytes in some circumstances.
These two reasons may be enough for the higher readings on the 64bit box.

Has anyone else noticed this phenomenon..

[meton_magis]

Does arch linux use precompiled binaries, like Yum or Apt? or do you compile stuff for your system like Portage?

are you using the same system? or are there differences in physical ram between the boxes?

[Rubberman]

All addressses are 64-bits in size, including function addresses, etc. This will make a big difference in memory footprint as far as the basic OS and UI is concerned, and that is probably what is causing the difference in memory usage between the 32-bit and 64-bit versions of the same OS. Compiler options are also important, but I think not the likely cause that you see here. A lot has to do also with what services are running. I know that when I run Windows XP in a non-VM environment, it takes at least 200MB to run in 32-bit mode, usually more. Shutting down unnecessary services helps, in any system case.

One other thing to consider is that how you measure system memory usage also matters. Tools such as 'top' and 'free' show how much memory is utilized, but a lot of that is buffer/cache data that the OS holds onto in order to speed performance (accessing data and starting applications) but are not really part of the resident set size of the system at that time. My general experience is that a Linux desktop running the same number and types of services and applications as Windows takes a bit less, and sometimes a lot less, memory than Windows.