• Johannes Weiner's avatar
    proc: revert /proc/<pid>/maps [stack:TID] annotation · 65376df5
    Johannes Weiner authored
    Commit b7643757
    
     ("procfs: mark thread stack correctly in
    proc/<pid>/maps") added [stack:TID] annotation to /proc/<pid>/maps.
    
    Finding the task of a stack VMA requires walking the entire thread list,
    turning this into quadratic behavior: a thousand threads means a
    thousand stacks, so the rendering of /proc/<pid>/maps needs to look at a
    million combinations.
    
    The cost is not in proportion to the usefulness as described in the
    patch.
    
    Drop the [stack:TID] annotation to make /proc/<pid>/maps (and
    /proc/<pid>/numa_maps) usable again for higher thread counts.
    
    The [stack] annotation inside /proc/<pid>/task/<tid>/maps is retained, as
    identifying the stack VMA there is an O(1) operation.
    
    Siddesh said:
     "The end users needed a way to identify thread stacks programmatically and
      there wasn't a way to do that.  I'm afraid I no longer remember (or have
      access to the resources that would aid my memory since I changed
      employers) the details of their requirement.  However, I did do this on my
      own time because I thought it was an interesting project for me and nobody
      really gave any feedback then as to its utility, so as far as I am
      concerned you could roll back the main thread maps information since the
      information is available in the thread-specific files"
    Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
    Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
    Cc: Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com>
    Cc: Shaohua Li <shli@fb.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    65376df5
util.c 11.4 KB