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

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Message-ID: <5445D978.5060609@huawei.com>
Date:	Tue, 21 Oct 2014 11:56:40 +0800
From:	Wang Nan <wangnan0@...wei.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
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

On 2014/10/16 22:55, Arnaldo Carvalho de Melo wrote:
> 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

So what's your opinion on these two patches?

>>
>> 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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