From: Steven Rostedt <rostedt@goodmis.org>
To: Douglas Anderson <dianders@chromium.org>
Cc: Ingo Molnar <mingo@redhat.com>,
Jason Wessel <jason.wessel@windriver.com>,
Daniel Thompson <daniel.thompson@linaro.org>,
kgdb-bugreport@lists.sourceforge.net,
Brian Norris <briannorris@chromium.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] tracing: kdb: Allow ftdump to skip all but the last few lines
Date: Wed, 13 Mar 2019 09:47:01 -0400 [thread overview]
Message-ID: <20190313094701.06b4e93d@gandalf.local.home> (raw)
In-Reply-To: <20190312232528.4fa0b806@oasis.local.home>
On Tue, 12 Mar 2019 23:25:28 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:
> 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.
>
Note, I pulled in patch 1 into my queue. So you only need to resend
this patch.
-- Steve
next prev parent reply other threads:[~2019-03-13 13:47 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-08 19:32 [PATCH v2 1/2] tracing: kdb: Fix ftdump to not sleep Douglas Anderson
2019-03-08 19:32 ` [PATCH v2 2/2] tracing: kdb: Allow ftdump to skip all but the last few lines Douglas Anderson
2019-03-13 3:25 ` Steven Rostedt
2019-03-13 13:47 ` Steven Rostedt [this message]
2019-03-08 20:19 ` [PATCH v2 1/2] tracing: kdb: Fix ftdump to not sleep Steven Rostedt
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