[ltt-dev] Mini Design and Roadmap of LTT-Kdump

[Lai Jiangshan]

Mini Design and Roadmap of LTT-Kdump

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	People in enterprise need to be able to diagnose why the system
failed. Failing once is acceptable from a customer perspective, but
failing again isn't. In this case, being able to extract the last events
before the crash can be very valuable and helps solving the problems
before they happen again.

	Create tools to simplify extraction of traces from crashed kernel.
The core file of crashed kernel is provided by kdump.
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	We will implement it. This tool include two parts.

Part1: Core-file analyser.
	Analyse(needs kernel-debuginfo) the core-file and read
ltt-relay files.
	This part will use elf-libs for analysing, but we use crash(8)
instead at first. crash(8) can simplify this work and crash(8) can perform
on a compressed core-file(http://sourceforge.net/projects/makedumpfile/).
	When we use crash(8), we will write a gdb script for analysing.
crash(8) loads this gdb script, core-file and kernel-debuginfo then listens
to a pipe and does works.
	crash(8) works very well when pages are vmap()ed into to a continuous
memmory region. But ltt-relay's pages are not vmap()ed, it'll very slow.
so we may use elf-libs or enhance crash(8) at last.

Part2: ltt-relay extracter
	Extracter calls analyser's API to travel the debugfs tree in core-file,
and copies all ltt-relay files to the disk. The written files are the same
format exactly as the files what lttd writes, so we can use lttv or other
lttng tools to read the events.


Any comments and ideas are welcome!

Thanks, Lai