Minecraft version: 1.4.6
Forge version: minecraftforge-universal-1.4.6-6.5.0.471.zip
Other mods installed: Rei's Minimap (v3.2_06), Optifine (1.4.6_HD_U_A2)
Problem: When running without Forge, I experience a memory inflation of approximately 100MB/s (As seen on the F3 screen), but when Forge is installed (And nothing is in /coremods or /mods), that number jumps to nearly 1500MB/s. Even with Optifine installed, this massive memory allocation causes my game to lag to nearly unplayable levels, forcing me to switch to Tiny render distance or uninstall Forge in order to play once again.
Log file associated with a test run: http://pastebin.com/qLbNMHUd
EDIT: I am currently using Java Runtime Environment 7u3 64-bit.