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[Michi Henning <michi.henning@xxxxxxxxxxxxx>]

** Changed in: unity-scopes-api (Ubuntu)
     Assignee: (unassigned) => Michi Henning (michihenning)

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https://bugs.launchpad.net/bugs/1364464

Title:
  unity8-dash has a thread that is polling rather rapidly on epoll wait

Status in “unity-scopes-api” package in Ubuntu:
  New
Status in “unity-scopes-shell” package in Ubuntu:
  New
Status in “unity8” package in Ubuntu:
  Incomplete

Bug description:
  one of the threads to unity8-dash is creating quite a few wakeups per
  second:

  # eventstat 60 1

   Event/s PID   Task            Init Function             Callback
     13.02  2812 scopes_ng::Scop hrtimer_start_range_ns    hrtimer_wakeup

  process 2812 is a thread of unity8-dash

  attaching strace to the thread we see:

  root@ubuntu-phablet:/proc# strace -p 2812 
  Process 2812 attached
  clock_gettime(CLOCK_MONOTONIC, {925, 47970238}) = 0
  epoll_wait(57, {}, 256, 115)            = 0
  clock_gettime(CLOCK_MONOTONIC, {925, 165670469}) = 0
  socket(PF_LOCAL, SOCK_STREAM|SOCK_CLOEXEC, 0) = 50
  fcntl64(50, F_GETFL)                    = 0x2 (flags O_RDWR)
  fcntl64(50, F_SETFL, O_RDWR|O_NONBLOCK) = 0
  connect(50, {sa_family=AF_LOCAL, sun_path="/run/user/32011/zmq/priv/clickscope"}, 110) = -1 ENOENT (No such file or directory)
  close(50)                               = 0
  clock_gettime(CLOCK_MONOTONIC, {925, 174626930}) = 0
  epoll_wait(57, {}, 256, 39)             = 0
  clock_gettime(CLOCK_MONOTONIC, {925, 215561930}) = 0
  socket(PF_LOCAL, SOCK_STREAM|SOCK_CLOEXEC, 0) = 50
  fcntl64(50, F_GETFL)                    = 0x2 (flags O_RDWR)
  fcntl64(50, F_SETFL, O_RDWR|O_NONBLOCK) = 0
  connect(50, {sa_family=AF_LOCAL, sun_path="/run/user/32011/zmq/priv/clickscope"}, 110) = -1 ENOENT (No such file or directory)
  close(50)                               = 0
  clock_gettime(CLOCK_MONOTONIC, {925, 222932007}) = 0
  epoll_wait(57, {}, 256, 65)             = 0
  clock_gettime(CLOCK_MONOTONIC, {925, 290266777}) = 0
  socket(PF_LOCAL, SOCK_STREAM|SOCK_CLOEXEC, 0) = 50
  fcntl64(50, F_GETFL)                    = 0x2 (flags O_RDWR)
  fcntl64(50, F_SETFL, O_RDWR|O_NONBLOCK) = 0

  ..ad infinitum...

  the epoll_wait() is sleeping a very short while before a connect to a
  clickscope named socket path is attempted over and over again. Is this
  rapid polling really necessary?   It's contributing to 0.50%-1.00% of
  the CPU load of the phone.

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