linux-kernel - Re: [PATCH] perf tools: fix incorrect header string

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Message-ID: <20141016145504.GW3198@kernel.org>
Date:	Thu, 16 Oct 2014 11:55:04 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	zhangzhiqiang.zhang@...wei.com, peifeiyue@...wei.com
Subject: Re: [PATCH] perf tools: fix incorrect header string

Em Thu, Oct 16, 2014 at 11:21:13AM +0800, Wang Nan escreveu:
> On 2014/10/15 23:13, Arnaldo Carvalho de Melo wrote:
> > Em Wed, Oct 15, 2014 at 11:28:53AM +0800, Wang Nan escreveu:
> >> Commit fbe96f29 (perf tools: Make perf.data more self-descriptive)
> >> read '/proc/cpuinfo' to form cpu descriptor. For ARM, it finds
> >> 'Processor' field. It is correct when the patch merged, but due to
> >> commit b4b8f770 (ARM: kernel: update cpuinfo to print all online CPUs
> >> features), the corresponding information becomes 'model name' field.
> >>
> >> This patch simply corrects it.
> > 
> > It doesn't :-)
> > 
> > It makes it work with kernels >= b4b8f770, and fail with older kernels.
> > 
> > We need to somehow figure out where the right information is regardless
> > of the kernel.
> > 
> > - Arnaldo
> >  
> 
> However it is a real problem. Look at output on arm platform at the
> bottom of this mail, especially  "cpudesc", "total memory" and "cmdline" field.

Yeah, I haven't said it wasn't a problem, just that the proposed fix
wasn't enough.

- Arnaldo
 
> By further debugging I found that the real problem resides in return value checking
> when write header error. Please see my other patches:
> 
> https://lkml.org/lkml/2014/10/15/612
> https://lkml.org/lkml/2014/10/15/611
> 
> I think at least one of them is required.
> 
> Thanks.
> 
> >> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> >> ---
> >>  tools/perf/perf-sys.h | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/tools/perf/perf-sys.h b/tools/perf/perf-sys.h
> >> index 937e432..4293970 100644
> >> --- a/tools/perf/perf-sys.h
> >> +++ b/tools/perf/perf-sys.h
> >> @@ -113,7 +113,7 @@
> >>  #define mb()		((void(*)(void))0xffff0fa0)()
> >>  #define wmb()		((void(*)(void))0xffff0fa0)()
> >>  #define rmb()		((void(*)(void))0xffff0fa0)()
> >> -#define CPUINFO_PROC	"Processor"
> >> +#define CPUINFO_PROC	"model name"
> >>  #endif
> >>  
> >>  #ifdef __aarch64__
> >> -- 
> >> 1.8.4
> 
> 
> 
> bash-4.2# perf record ls
> ...
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.001 MB perf.data (~36 samples) ]
> bash-4.2# perf report --stdio --header
> Error:
> The perf.data file has no samples!
> # ========
> # captured on: Fri Sep 12 10:09:10 2014
> # hostname : arma15el
> # os release : 3.17.0+
> # perf version : 3.10.53
> # arch : armv7l
> # nrcpus online : 4
> # nrcpus avail : 1
> # cpudesc : (null)
> # total memory : 0 kB
> # cmdline :
> # event : name = cycles, type = 0, config = 0x0, config1 = 0x0, config2 = 0x0, excl_usr = 0, excl_kern = 0, excl_host = 0, excl_guest = 1, precise_ip = 0
> # pmu mappings: not available
> # ========
> #
> 
> 
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