Re: [PATCH v9 3/3] tracing/Documentation: Add a section about backup instance

[Steven Rostedt]

On Wed, 1 Apr 2026 12:15:41 +0900
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> wrote:

> > > +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  
> > 
> > The above didn't actually work well without my patch to enable events on
> > the persistent ring buffer with the backup. But keep it, as it will work
> > with my patch ;-)  
> 
> Ah, thanks!
> Let me rebase on it.

Well, my patch hasn't been added yet ;-)  But don't change anything. When
this goes upstream both patches should have been applied.

-- Steve