Hugepages backing file map0 is not being unlinked

https://bugs.dpdk.org/show_bug.cgi?id=575

            Bug ID: 575
           Summary: Hugepages backing file map0 is not being unlinked
           Product: DPDK
           Version: 20.11
          Hardware: All
                OS: All
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: Normal
         Component: core
          Assignee: [email protected]
          Reporter: [email protected]

Target Milestone: ---

I am not sure if this is a bug or simply part of the design so please, bear with me. :)

I noticed that whenever application - which uses DPDK's mem components for mapping hugepages - exits there's always one hugepages backing file left under hugetlbfs mount. Specifically, it's the file that's mapped under the very begging of the address space. E.g. where base-virtaddr is set to 0x200000000000:

200000200000-200000400000 rw-s 00000000 00:29 18115803 /dev/hugepages/spdk_pid1806446map_0

When the unlinking starts upon existing, everything down to map1 (0x200000400000) is unlinked but map0 remains. This is not the case when --huge-unlink is used during the init part (all backing files are unlinked at the start then, including map0).

This doesn't seem to be a big deal in itself, but depending on what size of hugepages we are using this may leave different footprint (e.g. we start 3 apps simultaneously, each one uses 1G hugepages. When they all exit, 3G of hugepages may be still in use). I can see that there's also a cleanup routine which is fired upon starting the app, to make sure that any lingering backing files are removed, but still. :)

Any hints on why this might be the case would be appreciated. :)

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