I understand the idea, but I don't have a lot of faith in the kernel to make the right decision under memory pressure--and neither do server application develop

I understand the idea, but I don't have a lot of faith in the kernel to make the right decision under memory pressure--and neither do server application developers, hence the proliferation of massive userland disk caches in processes. The amount of allocated memory that the kernel can find to discard on a no-swap system is fairly small, so I'm somewhat relying on the rogue program overrunning the point of blowing out the caches and going all the way to panic the system. Ideal tuning would probably also reserve some decent amount of space for file caches and slab but I'm not aware of any setting that does that. It's an entirely different story on laptops and development servers, where the workload varies widely, may contain large idle heap allocations worth swapping, and manually configuring memory usage isn't practical.