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authorJohannes Weiner <hannes@cmpxchg.org>2016-02-03 01:57:29 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2016-02-03 17:28:43 +0100
commit65376df582174ffcec9e6471bf5b0dd79ba05e4a (patch)
tree60c4841a00605605bf8c315783ed48648333e865 /Documentation/networking/pktgen.txt
parentnuma: fix /proc/<pid>/numa_maps for hugetlbfs on s390 (diff)
downloadlinux-65376df582174ffcec9e6471bf5b0dd79ba05e4a.tar.xz
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proc: revert /proc/<pid>/maps [stack:TID] annotation
Commit b76437579d13 ("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: Johannes 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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