touch-packages team mailing list archive

[Colin Ian King <1364464@xxxxxxxxxxxxxxxxxx>]

In 60 seconds, one can observe:

% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 44.51    2.250000        2139      1052           poll
 28.03    1.416574         366      3871           epoll_wait
 24.33    1.230000       10250       120           rt_sigtimedwait
  2.77    0.140000       70000         2           restart_syscall
  0.26    0.013026           2      6306           fcntl64
  0.04    0.002036           1      3153      3153 connect
  0.01    0.000655           0      3213           close
  0.01    0.000607           0      3213           socket
  0.01    0.000529           0      7134           clock_gettime
  0.01    0.000520           1      1026           write
  0.01    0.000352           0      1038        16 read
  0.00    0.000246           0       985           recvfrom
  0.00    0.000098           1       120           madvise
  0.00    0.000000           0        54           ioctl
  0.00    0.000000           0         6           gettimeofday
  0.00    0.000000           0       120           clone
  0.00    0.000000           0        25           mprotect
  0.00    0.000000           0         1           writev
  0.00    0.000000           0         1           sched_yield
  0.00    0.000000           0       120           rt_sigprocmask
  0.00    0.000000           0        15         5 futex
  0.00    0.000000           0         6           bind
  0.00    0.000000           0         6           getsockname
  0.00    0.000000           0        12           sendto
  0.00    0.000000           0        77        13 recvmsg
  0.00    0.000000           0       120           set_robust_list
------ ----------- ----------- --------- --------- ----------------
100.00    5.054643                 31796      3187 total

The 3153 failed connects are to named sockets that don't exist. That's a
rate of 52 PER SECOND.  This is rather ridiculous, we are meant to be
trying to make a low power phone last and not drain the battery on this
kind of rapid polling.

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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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