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Date: Wed, 6 Jul 2016 12:53:32 +0200
From: Jiri Olsa <jolsa@redhat.com>
To: Wang Nan <wangnan0@huawei.com>
Cc: acme@kernel.org, linux-kernel@vger.kernel.org, pi3orama@163.com,
        lizefan@huawei.com, Arnaldo Carvalho de Melo <acme@redhat.com>,
        He Kuang <hekuang@huawei.com>, Jiri Olsa <jolsa@kernel.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>, Nilay Vaish <nilayvaish@gmail.com>
Subject: Re: [PATCH v13 1/8] perf tools: Drop redundant evsel->overwrite
 indicator
Message-ID: <20160706105332.GA26517@krava>
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On Mon, Jul 04, 2016 at 06:20:02AM +0000, Wang Nan wrote:

SNIP

> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 0fea724..3abe519 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -1359,6 +1359,9 @@ static int __perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus,
>  	int pid = -1, err;
>  	enum { NO_CHANGE, SET_TO_MAX, INCREASED_MAX } set_rlimit = NO_CHANGE;
>  
> +	if (perf_missing_features.write_backward && evsel->attr.write_backward)
> +		return -EINVAL;
> +
>  	if (evsel->system_wide)
>  		nthreads = 1;
>  	else
> @@ -1389,11 +1392,6 @@ fallback_missing_features:
>  	if (perf_missing_features.lbr_flags)
>  		evsel->attr.branch_sample_type &= ~(PERF_SAMPLE_BRANCH_NO_FLAGS |
>  				     PERF_SAMPLE_BRANCH_NO_CYCLES);
> -	if (perf_missing_features.write_backward) {
> -		if (evsel->overwrite)
> -			return -EINVAL;
> -		evsel->attr.write_backward = false;
> -	}

so we don't change the attr.write_backward anymore?
based on the kernel support.. 

we do it for other features, why not here? also changelog
did not mentioned it at all ;-)

thanks,
jirka