[erlang-bugs] Regression in erlang:system_monitor long_gc ?

Chris Newcombe <>
Wed Oct 22 22:21:57 CEST 2008


Hi OTP team,

I'm using  R12B-2  (erts 5.6.2).   I'm using erlang:system_monitor to
detect long_gc times.

I very often see long_gc times mis-reported as >4,200 seconds, e.g.

   system_monitor: {1224,701965,21022}: system_monitor: killing
<0.149.0> as received
{monitor,<0.149.0>,long_gc,[{timeout,4295002},{old_heap_block_size,0},{heap_block_size,6419485},{mbuf_size,0},{stack_size,32},{old_heap_size,0},{heap_size,2000144}]}

I searched the mailing-list archives, and someone else reported this
back in July
     http://www.erlang.org/pipermail/erlang-questions/2008-July/036388.html
but I couldn't find any response.

I found an entry in very old release notes an apparently identical bug
was fixed in R9.

   http://www.erlang.org/documentation/doc-5.5/erts-5.5/doc/html/notes_history.html
  1.9 ERTS 5.3.3
  When using erlang:system_monitor(Pid,{long_gc,Time}), and the GC
time exceeded 1 second, it sometimes erroneously showed up as about
4300 seconds. This bug has now been corrected.
Own Id: OTP-4903 Aux Id: seq8379

Please could this be fixed?  system_monitor is extremely useful in
production systems :)

many thanks,

Chris Newcombe



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