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Date: Wed, 18 Nov 2015 18:25:15 +0900 From: Namhyung Kim <namhyung@...il.com> To: Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org> CC: "Wangnan (F)" <wangnan0@...wei.com>, Jiri Olsa <jolsa@...nel.org>, Arnaldo Carvalho de Melo <acme@...nel.org>, lkml <linux-kernel@...r.kernel.org>, David Ahern <dsahern@...il.com>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, Milian Wolff <milian.wolff@...b.com> Subject: Re: [PATCH 2/3] perf tools: Add callchain order support for libunwind DWARF unwinder On November 18, 2015 5:25:25 PM GMT+09:00, Jiri Olsa <jolsa@...hat.com> wrote: >On Wed, Nov 18, 2015 at 02:41:14PM +0900, Namhyung Kim wrote: > >SNIP > >> > I'm not sure whether we can regard this behavior changing as a >bugfix? I >> > think >> > there may be some reason the original code explicitly avoid >creating an '0' >> > entry. >> >> I think callchain value being 0 is an error or marker for the end of >> callchain. So it'd be better avoiding 0 entry. >> >> But unfortunately, we have many 0 entries (and broken callchain after >> them) with fp recording on optimized binaries. I think we should >omit >> those callchains. >> >> Maybe something like this? >> >> >> >> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c >> index 5ef90be2a249..22642c5719ab 100644 >> --- a/tools/perf/util/machine.c >> +++ b/tools/perf/util/machine.c >> @@ -1850,6 +1850,15 @@ static int >thread__resolve_callchain_sample(struct thread *thread, >> #endif >> ip = chain->ips[j]; >> >> + /* callchain value inside zero page means it's broken, stop */ >> + if (ip < 4096) { >> + if (callchain_param.order == ORDER_CALLER) { >> + callchain_cursor_reset(&callchain_cursor); > >hum, do we want to throw away whatever we have till now? For caller order, yes. For callee order, everything after 0 value is garbage. So we need to discard any chains before the 0 for caller IMHO. Thanks Namhyung -- Sent from my Android device with K-9 Mail. Please excuse my brevity. -- 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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