[ltt-dev] about the problem of LTTng Events lost always occurred in sys_ioctl

Juntang Fu(David) juntang.fu at windriver.com
Fri Jan 7 01:52:59 EST 2011

Hi, Mathieu:
  I have a question about LTTng relay buffer management, could you help
me on it? thanks in advance.
  in my test case in a ARM target, I start a trace with normal mode, I
have found that always some events will be lost in cpu_0 channel, if I
enlarge the buffer size and number of buffers, the number of lost
events can be decreased. but when I check the traced logs, I have found
that all of the lost events always happen in the position following
with the events named sys_ioctl and kernel_syscall_exit(ret=54). please
see the attached picture to check it.
  So my confused question is that:
  if the sub buffer is not enough and the data are over written, then
the data lost should be random, right? does LTTng kernel buffer
management have some special handling with some events?

  My kernel version: 2.6.27
  LTTng version :    patch-


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