[question] how to figure out OOM reason? should dump slab/vmallocinfo when OOM?

[Jianguo Wu]

When OOM happen, will dump buddy free areas info, hugetlb pages info,
memory state of all eligible tasks, per-cpu memory info.
But do not dump slab/vmalloc info, sometime, it's not enough to figure out the
reason OOM happened.

So, my questions are:
1. Should dump slab/vmalloc info when OOM happen? Though we can get these from proc file,
but usually we do not monitor the logs and check proc file immediately when OOM happened.

2. /proc/$pid/smaps and pagecache info also helpful when OOM, should also be dumped?

3. Without these info, usually how to figure out OOM reason?

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