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[86.9.19.6]) by smtp.gmail.com with ESMTPSA id r12sm2629537wrr.71.2019.03.20.03.50.30 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 20 Mar 2019 03:50:30 -0700 (PDT) Date: Wed, 20 Mar 2019 10:50:28 +0000 From: Daniel Thompson To: Douglas Anderson Cc: Steven Rostedt , Ingo Molnar , Jason Wessel , kgdb-bugreport@lists.sourceforge.net, Brian Norris , linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 3/3] tracing: kdb: Allow ftdump to skip all but the last few entries Message-ID: <20190320105028.6t6urpf344mljb2g@holly.lan> References: <20190319171206.97107-1-dianders@chromium.org> <20190319171206.97107-3-dianders@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190319171206.97107-3-dianders@chromium.org> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 19, 2019 at 10:12:06AM -0700, Douglas Anderson 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 data 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 > entries. Unfortunately it provides no way for you to know how many > entries 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 entries except the last few. This > allows you to quickly see what you want. > > Note that we also change the printout in ftdump to print the > (positive) number of entries actually skipped since that could be > helpful to know when you've specified a negative skip count. > > Signed-off-by: Douglas Anderson > --- > > Changes in v6: > - Keep tracing disabled between counting and dumping. > - Remove Daniel Thompson Ack due to changes between v5 and v6. ... and I'm very happy to replace it: Acked-by: Daniel Thompson Daniel.