Memory is called an incompressible resource. What does this mean in practice?

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Accepted Answer

Once allocated, the kernel cannot reclaim memory gradually — it must kill the process to free the resource — CPU is compressible — you can throttle it. Memory is incompressible — once allocated, the kernel can't reclaim it without killing the process. This is why exceeding CPU limits causes throttling but exceeding memory limits causes OOMKill.

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The kernel compresses memory pages when usage is high, trading CPU time for reduced memory footprint

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Memory limits are enforced at allocation time — the kernel blocks new allocations before they exceed the limit

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Memory is pinned to a single CPU socket and cannot be moved between NUMA nodes under pressure

Memory is called an incompressible resource. What does this mean in practice?

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