linux-kernel - Re: [PATCH v11 1/3]: perf util: map data buffer for preserving collected data

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Message-ID: <20181008151258.GI18757@krava>
Date:   Mon, 8 Oct 2018 17:12:58 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v11 1/3]: perf util: map data buffer for preserving
 collected data

On Mon, Oct 08, 2018 at 05:43:38PM +0300, Alexey Budankov wrote:
> Hi,
> 
> On 08.10.2018 15:38, Jiri Olsa wrote:
> > On Mon, Oct 08, 2018 at 03:03:18PM +0300, Alexey Budankov wrote:
> <SNIP>
> >>
> >> Well, let's go with stub functions design as opposite to pure 
> >> conditional compilation. However this may, probably, result in 
> >> unintended Perf tool binary size growth, even if NO_AIO is 
> >> defined during compilation.
> > 
> > hum, empty functions are be optimized out
> 
> Yes, but there will be references to stubs in else branch of 
> record__mmap_read_evlist() so I am not sure that *all* compilers 
> are smart enough to recognize and still optimize it out.

well, kernel is doing that and it seem to be fine,
so I wouldn't worry about it

jirka