linux-kernel - Re: [PATCH] perf diff: Report noisy for cycles diff

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Date:   Wed, 17 Jul 2019 20:57:07 +0800
From:   "Jin, Yao" <yao.jin@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH] perf diff: Report noisy for cycles diff



On 7/16/2019 4:51 PM, Jiri Olsa wrote:
> On Fri, Jul 12, 2019 at 03:53:55PM +0800, Jin Yao wrote:
>> This patch prints the stddev and hist for the cycles diff of
>> program block. It can help us to understand if the cycles diff
>> is noisy or not.
> 
> I'm getting compile error:
> 
>    CC       builtin-diff.o
> builtin-diff.c: In function ‘compute_cycles_diff’:
> builtin-diff.c:712:10: error: taking the absolute value of unsigned type ‘u64’ {aka ‘long unsigned int’} has no effect [-Werror=absolute-value]
>    712 |          labs(pair->block_info->cycles_spark[i] -
>        |          ^~~~
> cc1: all warnings being treated as errors
> mv: cannot stat './.builtin-diff.o.tmp': No such file or directory
> 
> 

Oh, sorry about that. My gcc (gcc version 7.4.0 (Ubuntu 
7.4.0-1ubuntu1~18.04.1)) didn't report this error. :(

u64 - u64 is u64. I should define it as s64.

Thanks for reminding me.

Thanks
Jin Yao

> jirka
>