On Thu, 29 Jan 2026 15:19:00 -0500 Steven Rostedt <[email protected]> wrote:
> 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" Ah, thanks, > > > +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 ^ the "boot_map". > > Thus the user > > > +without stopping trace. > > stopping the trace. OK. > > > + > > +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 ;-) Thanks! > > -- Steve -- Masami Hiramatsu (Google) <[email protected]>
