<html><body><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; color: #000000"><div>Hi Martin,<br></div><div><br data-mce-bogus="1"></div><div>The main limitation LTTng currently has for early boot tracing is that<br data-mce-bogus="1"></div><div>you need to first spawn a lttng-sessiond user-space process, and setup<br data-mce-bogus="1"></div><div>tracing, before you can actually do any tracing. As long as you can<br data-mce-bogus="1"></div><div>fit within those constraints, you should be OK.<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>If you really want to trace earlier than that, you might have to create<br data-mce-bogus="1"></div><div>a dedicated early-boot tracing module that would setup tracing<br data-mce-bogus="1"></div><div>buffers into a "dummy" session which exists only within lttng-modules,</div><div>and then allow sessiond to later hook on those buffers when user-space</div><div>is ready. Nothing exists for this at the moment. Note that since</div><div>lttng-modules master (upcoming 2.8), you can now build lttng-modules</div><div>into your kernel image, this might be useful for you. See the "kernel</div><div>built-in support" section in</div><div>https://github.com/lttng/lttng-modules/blob/master/README.md<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>Since LTTng 2.0, we have left early boot tracing to other tools, such</div><div>as Ftrace, which target kernel developers use-cases, and focused</div><div>more on tracing of the system in its execution phases which are more</div><div>relevant to application developers.<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>If you want to go ahead and create a LTTng modules module that<br data-mce-bogus="1"></div><div>allow early boot tracing, I'd be happy to provide ideas and review.<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>Thanks,<br data-mce-bogus="1"></div><div><br data-mce-bogus="1"></div><div>Mathieu<br data-mce-bogus="1"></div><div><br></div><span id="zwchr" data-marker="__DIVIDER__">----- On Feb 25, 2016, at 3:56 PM, Martin Townsend <mtownsend1973@gmail.com> wrote:<br></span><div data-marker="__QUOTED_TEXT__"><blockquote style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><div dir="ltr"><div><div>Hi,<br><br></div>This is a bit of a long shot but does LTTng allow you trace boot?<br><br>I'm seeing a weird problem where if I boot with systemd-bootchart if boots faster than just using systemd as the init process. I created my own init process based on systemd-bootchart and worked out it was down to the fact it called nanosleep, so I now have my own init process which hands over to systemd and creates a child that nanosleeps for the boot duration. I would really like to trace/profile the scheduler and hrtimers understand what's happening and try and get a proper fix :) Even if it means a bit of hacking kernel/LTTng, I would be willing to do this.<br><br></div>Many Thanks, Martin.<br></div>
<br>_______________________________________________<br>lttng-dev mailing list<br>lttng-dev@lists.lttng.org<br>http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev<br></blockquote></div><br><div data-marker="__SIG_POST__">-- <br></div><div>Mathieu Desnoyers<br>EfficiOS Inc.<br>http://www.efficios.com</div></div></body></html>