On Wed, 28 Jan 2026 09:10:11 +0900 "Masami Hiramatsu (Google)" <[email protected]> wrote:
> From: Masami Hiramatsu (Google) <[email protected]> > > Add a section about backup instance to the debugging.rst. > > Signed-off-by: Masami Hiramatsu (Google) <[email protected]> > --- > Documentation/trace/debugging.rst | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/Documentation/trace/debugging.rst > b/Documentation/trace/debugging.rst > index 4d88c346fc38..73e2154bcf98 100644 > --- a/Documentation/trace/debugging.rst > +++ b/Documentation/trace/debugging.rst > @@ -159,3 +159,22 @@ If setting it from the kernel command line, it is > recommended to also > disable tracing with the "traceoff" flag, and enable tracing after boot up. > Otherwise the trace from the most recent boot will be mixed with the trace > from the previous boot, and may make it confusing to read. > + > +Using a backup instance for keeping previous boot data > +------------------------------------------------------ > + > +It is also possible to record trace data at system boot time by specifying > +events with the persistent ring buffer, but in this case the data before the > +reboot will be lost before it can be read. This problem can be solved by a > +backup instance. From the kernel command line:: > + > + reserve_mem=12M:4096:trace trace_instance=boot_map@trace,sched,irq > trace_instance=backup=boot_map > + > +When the boot up, the previous data in the`boot_map` is copied to "backup" s/When the boot up/On boot up/ copied to the "backup" > +instance, and the "sched:*" and "irq:*" events for current boot are traced on for the current boot are traced in > +"boot_map". Thus user can read the previous boot data from the "backup" > instance Thus the user > +without stopping trace. stopping the trace. > + > +Note that this "backup" instance is readonly, and will be removed > automatically > +if you clear the trace data or read out all trace data from "trace_pipe" or > +"trace_pipe_raw" files. > \ No newline at end of file Definite articles are a pain ;-) -- Steve
