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rostedt

Steven Rostedt

With my new persistent memory mapped ring buffer, were I can retrieve the tracing buffer from the previous boot that crashed, I was able to debug a recent issue. To do this, I added code to allow trace_printk() to be directed to the persistent ring buffer, along with enabling the printk console trace event (writes all printk()s to the tracing ring buffer), I was able to get the perfect idea of what was happening that lead up to the crash!

https://lore.kernel.org/lkml/20240823013902.135036960@goodmis.org/

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a3f@fosstodon.org

Ahmad Fatoum

Reply to @rostedt

@rostedt I am curious how the new persistent ring buffer differs from CONFIG_PSTORE_FTRACE=y + CONFIG_PSTORE_RAM=y. I guess no ECC, but transparent appending to the ring buffer?

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rostedt

Steven Rostedt

Reply to @a3f@fosstodon.org
@a3f yep. The biggest difference is the interface. It shows up as another instance in the tracefs file system that can be enabled or read pretty much like any other instance. You can even use `trace-cmd` to start it, read it and even extract it. Although it will need some tweaks for extraction.
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