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Peter Anvin" , Masami Hiramatsu , Mathieu Desnoyers , "Paul E. McKenney" Subject: Re: [PATCH] x86/tracing: introduce enter/exit tracepoint pairs for page faults Message-ID: <20250418213945.GJaALGod4-j86Squ43@fat_crate.local> References: <20250414205441.GGZ_12Eew18bGcPTG0@fat_crate.local> <20250414182050.213480aa@gandalf.local.home> <20250416174714.GGZ__tIi3yNzNKoKFE@fat_crate.local> <20250416140115.5b836b33@gandalf.local.home> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250416140115.5b836b33@gandalf.local.home> On Wed, Apr 16, 2025 at 02:01:15PM -0400, Steven Rostedt wrote: > The above was created by: > > # trace-cmd sqlhist -e -n user_faults SELECT TIMESTAMP_DELTA_USECS as delta FROM page_fault_user_enter as start JOIN \ > page_fault_user_exit as end ON start.common_pid = end.common_pid Pfff, that's SQL. You're too old fashioned - you need an AI thing now :-P So tell me: I as a silly user, how do I figure out how to use trace-cmd? I guess it has docs somewhere... And apparently I need trace-cmd now - I can't type all that into sysfs... Or I guess I can use trace-cmd to generate the commands and then I can echo them into the target machine. I.e., ftrace still doesn't need a special tool to be used... > This was just a simple example. I rather see where in the kernel it happens. > I can still use the synthetic events and user stack trace to find where the > big faults occur. Right, so it would be great to have the actual use case in a patch's commit message... i.e., why is a patch important. > > Now if only that info were in the commit message along with the usage scenario > > so that people can *actually* do what you guys are bragging about... > > I plan on adding things like this to Documentation/trace/debugging.rst > > I need to get time out to add a bunch of helpful tricks there. Yap, please. I have to admit I was able to catch a trace for tglx using only the ftrace documentation we have so it must be good. But moar is better. :-P Thx man! -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette