Date: Wed, 18 Nov 2015 09:25:25 +0100
From: Jiri Olsa <jolsa@redhat.com>
To: Namhyung Kim <namhyung@kernel.org>
Cc: "Wangnan (F)" <wangnan0@huawei.com>, Jiri Olsa <jolsa@kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        lkml <linux-kernel@vger.kernel.org>, David Ahern <dsahern@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>,
        Milian Wolff <milian.wolff@kdab.com>
Subject: Re: [PATCH 2/3] perf tools: Add callchain order support for
 libunwind DWARF unwinder
Message-ID: <20151118082525.GC5416@krava.brq.redhat.com>
References: <1447772739-18471-1-git-send-email-jolsa@kernel.org>
 <1447772739-18471-3-git-send-email-jolsa@kernel.org>
 <564BFAD4.8060909@huawei.com>
 <20151118054114.GQ7062@sejong>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20151118054114.GQ7062@sejong>
User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1391
Lines: 41

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?

jirka
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/