what's the point of having a bunch of ram sitting around doing nothing, I would rather have a system that had zero free ram but managed its address space well, so that changing ram usage was painless. why pay good money to have hardware sitting idle?.
The same reason I refill my car's gas tank long before it hits zero; low/no resource problems range from irritating to catastrophic. Unused RAM isn't wasted, it's headroom.
But you OS doesn’t have to find a petrol station it may not even be able to reach — it can just swap to SSD or the best - swap to RAM itself by compressing pages (zram on linux and mac does it as well). Empty RAM is seriously wasted unless it is some embedded system where you are managing memory and need some strange latency requirements.
As described below, that's what's supposed to happen, but the default kernel configuration in mainstream distros will happily hold onto caches while swapping so hard to be unusable, or worse, loosing the OOM killer to wreak havoc on my workspace. This is unacceptable, and this is why I want headroom.
At the end of the day, if my system wildly misbehaves under high memory pressure, and forcing the pressure down resolves the misbehavior (or keeping a certain amount of headroom prevents it from happening outright), "linux ate my ram" is an accurate description of what happened and no amount of tut-tutting telling me that it doesn't work the way I just got done seeing it work changes that.
I'll give zram a try, but the problem here is poor usage of memory (both in priority and badly-behaved bloatware), not quantity of memory available. I'm not a kernel developer, I shouldn't have to dork around with these kinds of knobs to get sane behavior.
