Messages in this thread | | | Date | Tue, 12 Mar 2019 23:25:28 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH v2 2/2] tracing: kdb: Allow ftdump to skip all but the last few lines |
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On Fri, 8 Mar 2019 11:32:05 -0800 Douglas Anderson <dianders@chromium.org> wrote:
> The 'ftdump' command in kdb is currently a bit of a last resort, at > least if you have lots of traces turned on. It's going to print a > whole boatload of lines out your serial port which is probably running > at 115200. This could easily take many, many minutes. > > Usually you're most interested in what's at the _end_ of the ftrace > buffer, AKA what happened most recently. That means you've got to > wait the full time for the dump. The 'ftdump' command does attempt to > help you a little bit by allowing you to skip a fixed number of lines. > Unfortunately it provides no way for you to know how many lines you > should skip. > > Let's do similar to python and allow you to use a negative number to > indicate that you want to skip all lines except the last few. This > allows you to quickly see what you want.
Why not just read how many entries are in the ring buffer and return that?
cnt = 0; for_each_cpu(cpu, tr->tracing_cpumask) cnt += ring_buffer_entries_cpu(tr->trace_buffer, cpu); return cnt;
The output will print out one entry per line.
-- Steve
> > Signed-off-by: Douglas Anderson <dianders@chromium.org> > --- >
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