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Date: Fri, 18 Jan 2008 22:55:27 -0500 (EST) From: Steven Rostedt <rostedt@...dmis.org> To: "Frank Ch. Eigler" <fche@...hat.com> cc: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>, LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>, Linus Torvalds <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Christoph Hellwig <hch@...radead.org>, Gregory Haskins <ghaskins@...ell.com>, Arnaldo Carvalho de Melo <acme@...stprotocols.net>, Thomas Gleixner <tglx@...utronix.de>, Tim Bird <tim.bird@...sony.com>, Sam Ravnborg <sam@...nborg.org>, Steven Rostedt <srostedt@...hat.com>, Paul Mackerras <paulus@...ba.org>, Daniel Walker <dwalker@...sta.com> Subject: Re: [RFC PATCH 16/22 -v2] add get_monotonic_cycles On Fri, 18 Jan 2008, Frank Ch. Eigler wrote: > > All this complexity is to be justified by keeping the raw prev/next > pointers from being sent to a naive tracer? It seems to me way out of > proportion. Damn, and I just blew away all my marker code for something like this ;-) Actually, you just gave me a great idea that I think can help all of us. OK, Mathieu may not be in total agreement, but I think this is the ultimate compromise. We have in sched.c the following marker: trace_mark(kernel_sched_scheduler, "prev %p next %p", prev, next); Then Mathieu can add in some code somewhere (or a module, or something) ret = marker_probe_register("kernel_sched_scheduler", "prev %p next %p", pretty_print_sched_switch, NULL); static void pretty_print_sched_switch(const struct marker *mdata, void *private_data, const char *format, ...) { va_list ap; struct task_struct *prev; struct task_struct *next; va_start(ap, format); prev = va_arg(ap, typeof(prev)); next = va_arg(ap, typeof(next)); va_end; trace_mark(kernel_pretty_print_sched_switch, "prev_pid %d next_pid %d prev_state %ld", prev->pid, next->pid, prev->state); } Then LTTng on startup could arm the normal kernel_sched_switch code and have the user see the nice one. All without adding any more goo or overhead to the non tracing case, and keeping a few critical markers with enough information to be useful to other tracers! Thoughts? -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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