Diagnosing and Fixing Memory Issues

[Mon Feb 08 17:10:52 2010] [notice] child pid 39479 exit signal Illegal instruction (4)
[Mon Feb 08 17:10:53 2010] [notice] child pid 39510 exit signal Illegal instruction (4)
[Sun Feb 14 05:43:24 2010] [error] server reached MaxClients setting, consider raising the MaxClients setting
[Sun Feb 14 12:38:28 2010] [notice] child pid 93038 exit signal Segmentation fault (11)
[Sun Feb 14 12:40:27 2010] [notice] child pid 92895 exit signal Segmentation fault (11)
[Sun Feb 14 12:50:16 2010] [notice] child pid 92968 exit signal Segmentation fault (11)
Feb 14 20:00:42 web020 kernel: swap_pager_getswapspace(8): failed
Feb 14 20:00:42 web020 kernel: swap_pager_getswapspace(16): failed
Feb 14 20:00:42 web020 kernel: swap_pager_getswapspace(12): failed
Feb 14 20:00:42 web020 kernel: swap_pager_getswapspace(16): failed
Feb 14 20:00:42 web020 kernel: swap_pager_getswapspace(12): failed
Feb 14 20:00:42 web020 kernel: swap_pager_getswapspace(16): failed
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Diagnosing and Fixing Memory Issues

When your VPS is running low on physical memory, it may start to "swap thrash." This means it's attempting to use your swap partition heavily instead of real RAM. We recommend you limit your swap partition size to 256 MB; heavy use of swap in a virtualized environment will cause major performance problems.

We strongly recommend running the 32-bit version of your distribution of choice, unless you have a specific reason to run the 64-bit version. The 32-bit version of your distro will use significantly less memory.
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5. Separate Out Virtual Swap Files Onto Separate Virtual Disks

Another way to increase performance on virtual machines is separate the swap files onto a separate host virtual and physical disks. In other words, currently, your swap file goes to the same virtual disk as all your other disk files. To increase performance, you would create a new virtual disk on a different host physical disk. You would then relocate your swap file to that new virtual disk. It won’t really be beneficial if you don’t relocate the new virtual disk to a new physical disk. This is a more advanced topic and complex process so I won’t go into all the details in this article. However, to change the location of your swap file, you go to Control Panel -> System -> Advanced Tab -> Performance Settings -> Advanced Tab -> Virtual Memory Change. Of course, you hope that you don’t have to do much swapping. To prevent swapping, you should increase the size of the memory allocated to the virtual machine (within the size of your physical RAM). Note, see “Upgrade your RAM”, below.
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Reference:
http://www.petri.co.il/virtual_increase_vmware_performance.htm
http://library.linode.com/troubleshooting/memory-networking