[1.1] libct/cg: support hugetlb rsvd #4077
Merged
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This is a backport of #4073 and #4086 to release-1.1 branch. Fixes #3859.
This adds support for
hugetlb.<pagesize>.rsvd
limiting and accounting.The previous non-rsvd max/limit_in_bytes does not account for reserved huge page memory, making it possible for a processes to reserve all the huge page memory, without being able to allocate it (due to cgroup restrictions).
In practice this makes it possible to successfully mmap more huge page memory than allowed via the cgroup settings, but when using the memory the process will get a SIGBUS and crash. This is bad for applications trying to mmap at startup (and it succeeds), but the program crashes when starting to use the memory. eg. postgres is doing this by default.
This also keeps writing to the old max/limit_in_bytes, for backward compatibility.
More info can be found here: https://lkml.org/lkml/2020/2/3/1153
(commit message mostly written by Odin Ugedal)