linux-kernel - Re: [PATCH V4 12/15] perf hists browser: add parameter to disable lost event warning

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Message-ID: <20180117035007.GA6901@danjae.aot.lge.com>
Date:   Wed, 17 Jan 2018 12:50:07 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     kan.liang@...el.com
Cc:     acme@...nel.org, peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org, wangnan0@...wei.com,
        jolsa@...nel.org, ak@...ux.intel.com, yao.jin@...ux.intel.com,
        kernel-team@....com
Subject: Re: [PATCH V4 12/15] perf hists browser: add parameter to disable
 lost event warning

Hi,

On Mon, Jan 15, 2018 at 12:20:48PM -0800, kan.liang@...el.com wrote:
> From: Kan Liang <kan.liang@...el.com>
> 
> For overwrite mode, the ringbuffer will be paused. The event lost is
> expected. It needs a way to notify the browser not print the warning.
> 
> It will be used later for perf top to disable lost event warning in
> overwrite mode. There is no behavior change for now.
> 
> Signed-off-by: Kan Liang <kan.liang@...el.com>
> ---

[SNIP]
> diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
> index 68146f4..e458920 100644
> --- a/tools/perf/ui/browsers/hists.c
> +++ b/tools/perf/ui/browsers/hists.c
> @@ -608,7 +608,8 @@ static int hist_browser__title(struct hist_browser *browser, char *bf, size_t si
>  	return browser->title ? browser->title(browser, bf, size) : 0;
>  }
>  
> -int hist_browser__run(struct hist_browser *browser, const char *help)
> +int hist_browser__run(struct hist_browser *browser, const char *help,
> +		      bool no_lost_event_warning)
>  {
>  	int key;
>  	char title[160];
> @@ -638,8 +639,9 @@ int hist_browser__run(struct hist_browser *browser, const char *help)
>  			nr_entries = hist_browser__nr_entries(browser);
>  			ui_browser__update_nr_entries(&browser->b, nr_entries);
>  
> -			if (browser->hists->stats.nr_lost_warned !=
> -			    browser->hists->stats.nr_events[PERF_RECORD_LOST]) {
> +			if (!no_lost_event_warning &&

Double negation is always confusing (at least for me), why not making
it "warn_lost_event"?

Thanks,
Namhyung


> +			    (browser->hists->stats.nr_lost_warned !=
> +			    browser->hists->stats.nr_events[PERF_RECORD_LOST])) {
>  				browser->hists->stats.nr_lost_warned =
>  					browser->hists->stats.nr_events[PERF_RECORD_LOST];
>  				ui_browser__warn_lost_events(&browser->b);