Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
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linux
tracing/Documentation: Add a section about backup instance
Add a section about backup instance to the debugging.rst.
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/177502548479.1311542.7062269603547001007.stgit@mhiramat.tok.corp.google.com
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
authored by
Masami Hiramatsu (Google)
and committed by
Steven Rostedt (Google)
e53ba177
eca33fda
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Documentation/trace/debugging.rst
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Documentation/trace/debugging.rst
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disable tracing with the "traceoff" flag, and enable tracing after boot up.
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Otherwise the trace from the most recent boot will be mixed with the trace
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from the previous boot, and may make it confusing to read.
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Using a backup instance for keeping previous boot data
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------------------------------------------------------
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It is also possible to record trace data at system boot time by specifying
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events with the persistent ring buffer, but in this case the data before the
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reboot will be lost before it can be read. This problem can be solved by a
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backup instance. From the kernel command line::
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reserve_mem=12M:4096:trace trace_instance=boot_map@trace,sched,irq trace_instance=backup=boot_map
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On boot up, the previous data in the "boot_map" is copied to the "backup"
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instance, and the "sched:*" and "irq:*" events for the current boot are traced
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in the "boot_map". Thus the user can read the previous boot data from the "backup"
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instance without stopping the trace.
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Note that this "backup" instance is readonly, and will be removed automatically
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if you clear the trace data or read out all trace data from the "trace_pipe"
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or the "trace_pipe_raw" files.