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Date: Tue, 17 Jan 2012 13:21:33 +0100 From: Ingo Molnar <mingo@...e.hu> To: Srikar Dronamraju <srikar@...ux.vnet.ibm.com> Cc: Jiri Olsa <jolsa@...hat.com>, Arnaldo Carvalho de Melo <acme@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Oleg Nesterov <oleg@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, LKML <linux-kernel@...r.kernel.org>, Linux-mm <linux-mm@...ck.org>, Andi Kleen <andi@...stfloor.org>, Christoph Hellwig <hch@...radead.org>, Steven Rostedt <rostedt@...dmis.org>, Roland McGrath <roland@...k.frob.com>, Thomas Gleixner <tglx@...utronix.de>, Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>, Arnaldo Carvalho de Melo <acme@...radead.org>, Anton Arapov <anton@...hat.com>, Ananth N Mavinakayanahalli <ananth@...ibm.com>, Jim Keniston <jkenisto@...ux.vnet.ibm.com>, Stephen Rothwell <sfr@...b.auug.org.au> Subject: Re: [PATCH v9 3.2 7/9] tracing: uprobes trace_event interface Have you tried to use 'perf probe' to achieve any useful instrumentation on a real app? I just tried out the 'glibc:free' usecase and it's barely usable. Firstly, the recording very frequently produces overruns: $ perf record -e probe_libc:free -aR sleep 1 [ perf record: Woken up 169 times to write data ] [ perf record: Captured and wrote 89.674 MB perf.data (~3917919 samples) ] Warning:Processed 1349133 events and lost 1 chunks! Using -m 4096 made it work better. Adding -g for call-graph profiling caused 'perf report' to lock up: perf record -m 4096 -e probe_libc:free -agR sleep 1 perf report [ loops forever ] I've sent a testcase to Arnaldo separately. Note that perf report --stdio appears to work. Regular '-e cycles -g' works fine, so this is a uprobes specific bug. Thanks, Ingo -- 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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