mm, proc: report PR_SET_THP_DISABLE in proc
David Rientjes has reported that commit 1860033237d4 ("mm: make
PR_SET_THP_DISABLE immediately active") has changed the way how we
report THPable VMAs to the userspace. Their monitoring tool is
triggering false alarms on PR_SET_THP_DISABLE tasks because it considers
an insufficient THP usage as a memory fragmentation resp. memory
pressure issue.
Before the said commit each newly created VMA inherited VM_NOHUGEPAGE
flag and that got exposed to the userspace via /proc/<pid>/smaps file.
This implementation had its downsides as explained in the commit message
but it is true that the userspace doesn't have any means to query for
the process wide THP enabled/disabled status.
PR_SET_THP_DISABLE is a process wide flag so it makes a lot of sense to
export in the process wide context rather than per-vma. Introduce a new
field to /proc/<pid>/status which export this status. If
PR_SET_THP_DISABLE is used then it reports false same as when the THP is
not compiled in. It doesn't consider the global THP status because we
already export that information via sysfs
Link: http://lkml.kernel.org/r/[email protected]
Fixes: 1860033237d4 ("mm: make PR_SET_THP_DISABLE immediately active")
Signed-off-by: Michal Hocko <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Reported-by: David Rientjes <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Paul Oppenheimer <[email protected]>
Cc: William Kucharski <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
2 files changed
