Just one very obtuse question: Can anyone think of a situation where providing more memory to a system running Linux (i386 / 32-bit, kernel 2.6.20-1) causes MySQL (specifically 5.0.27) to perform slower than it did with less memory using the same settings (same my.cnf file)?
I know windows XP and lesser flavors of Windows Server have problems when approaching 4GB, but I was a bit concerned when the MySQL environment began to exhibit unexpected behavior. Simply maximizing memory (2GB to 4GB) and changing no server settings I would expect performance to be roughly identical. Instead, MySQL appeared to not allocate as many bytes of RAM as previously and queries where taking longer, running at 100% CPU usage-- probably writing tmp tables to disk. Its just weird, isn’t it? Again, all I did was add more memory. I changed no server settings.
Happy ending, at any rate. I was able to spend a few hours tweaking settings and a couple of the queires in question to re-gain acceptable performance.