2022-09-13 08:16:46

by Paul Menzel

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Subject: `switch_ldt()` fills up trace file

Dear Linux folks,


Using `bootgraph.py -f -manual` [1] to generate the Linux CLI line for
tracing the boot, and changing `do_one_initcall` to `dell_init` to trace
`drivers/platform/x86/dell/dell-laptop.c`, `switch_ldt();` fills up the
trace file. Is that expected, and can I work around it?

```
# boot-091222-181507 dellxps139360 boot 5.19.0-1-amd64
# sysinfo | man:Dell Inc. | plat:XPS 13 9360 | cpu:Intel(R) Core(TM)
i7-7500U CPU @ 2.70GHz | bios:2.21.0 | biosdate:06/02/2022 | numcpu:4 |
memsz:15959616 | memfr:11084888 | os:Debian GNU/Linux bookworm/sid
# command | analyze_boot.py -f
# kparams | BOOT_IMAGE=/vmlinuz-5.19.0-1-amd64
root=UUID=fe58fd63-a3e1-4670-b648-45c6a324394a ro initcall_debug
log_buf_len=32M trace_buf_size=524288K trace_clock=global
trace_options=nooverwrite,funcgraph-abstime,funcgraph-cpu,funcgraph-duration,funcgraph-proc,funcgraph-tail,nofuncgraph-overhead,context-info,graph-time
ftrace=function_graph ftrace_graph_max_depth=5
ftrace_graph_filter=dell_init cryptomgr.notests
# tracer: function_graph
#
# TIME CPU TASK/PID DURATION
FUNCTION CALLS
# | | | | | | | |
| |
0.516713 | 0) systemd-1 | 1.671 us | switch_ldt();
0.516715 | 0) systemd-1 | 0.207 us | switch_ldt();
0.516716 | 0) systemd-1 | 0.170 us | switch_ldt();
[…]
```


Kind regards,

Paul


[1]: https://github.com/intel/pm-graph