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<p class="MsoNormal">Is anyone else using systemd-bootchart on a system that boots using an initial ramdisk? (e.g. like Fedora 41)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I am fighting with two issues and am looking for some advice.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">**1. systemd-bootchart stops too early**<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">According to “man systemd-bootchart”, the recommended way to invoke bootchart is via a kernel parameter:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> init=/usr/lib/systemd/systemd-bootchart<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">That parameter causes systemd-bootchart to be executed as the new init process when we switch into the real root filesystem.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">bootchart does run, but it stops too early.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">In /etc/systemd/bootchart.conf, I have bootchart configured to collect 1800 samples at a frequency of 10 samples per sec. It should run for about 3 minutes.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">When I login, the svg file is already present under /run/log (but the system has only been up for about 10 secs).<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Doing “grep bootchart /proc/*/cmdline” when I login shows that bootchart is not running.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">**2. systemd-bootchart errors out during switch root**<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">In this case, I have systemd-bootchart added to the initial ramdisk and execute it via the “rdinit” kernel parameter:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> rdinit=/usr/lib/systemd/systemd-bootchart<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">In the systemd-bootchart source, you can see that the first character of its argv[0] is changed to “@”, so bootchart should survive the switch-root killing spree.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Unfortunately, bootchart errors out during switch root because it wants to read /proc/schedstat and it is not available (I have an strace log confirming that).<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">There seems to be a time-of-check / time-of-use issue in the code -- it checks that the proc filesystem is available, but then when it goes to read /proc/schedstat the file is not there (ENOENT).<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Has anyone else come across these?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Should I open github issues?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I can try creating a PR to fix issue 2.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">-James M <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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