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0 pointsthe84722y ago0 comments

Aiming to please people who panic about their RSS numbers seems... misguided? It seems like worrying about RAM being "used" as file cache[0].

If you want to gauge whether your system is memory-limited look at the PSI metrics instead.

[0] https://www.linuxatemyram.com/

0 comments

nh22y ago

Those are not the same.

You can see cache usage in htop; it has a different colour.

With MADV_FREE, it looks like the process is still using the memory.

That sucks: If you have some server that's slow, you want to SSH into a server and see how much memory each process takes. That's a basic, and good, observability workflow. Memory leaks exist, and tools should show them easily.

The point of RES is to show resident memory, not something else.

If you change htop to show the correct memory, that'd fix the issue of course.

the8472OP2y ago

Well, RES is resident in physical memory. It just is marked so that the kernel can make reclaim it when it needs to. But until then it's resident. If you want to track leaks you need resident-and-in-use metric which may be more difficult to come by (probably requires scanning smaps?).

It's a case of people using the subtly wrong metrics and then trying to optimize tools chasing that metric rather than improving their metrics. That's what I'm calling misguided.

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