I would be surprised if managing disk cache by hand is going to beat the Linux cache allocator. RAM is never wasted, every byte not being used by an application

I would be surprised if managing disk cache by hand is going to beat the Linux cache allocator. RAM is never wasted, every byte not being used by an application is used by the kernel for disk cache. If you dedicate 2 gigabytes of it to the .cache folder than either it's going to be mostly empty and you're be causing more thrashing as the kernel unloads stuff it didn't need to, or it fills up and your system falls over when something tries to put a big temporary file in that folder.