linux-kernel - Re: [PATCH RFC V3 5/5] perf top: switch back to overwrite mode

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Message-ID: <20170925203604.GP4311@tassilo.jf.intel.com>
Date:   Mon, 25 Sep 2017 13:36:04 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     kan.liang@...el.com
Cc:     acme@...nel.org, peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org, jolsa@...nel.org,
        namhyung@...nel.org, adrian.hunter@...el.com,
        lukasz.odzioba@...el.com
Subject: Re: [PATCH RFC V3 5/5] perf top: switch back to overwrite mode

On Mon, Sep 25, 2017 at 01:23:08PM -0700, kan.liang@...el.com wrote:
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index 6a0d7ff..ef0b6b1 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -723,7 +723,10 @@ perf_mmap__read(struct perf_mmap *md, bool check_messup, u64 start,
>  		 * In either case, truncate and restart at 'end'.
>  		 */
>  		if (diff > md->mask / 2 || diff < 0) {
> -			fprintf(stderr, "WARNING: failed to keep up with mmap data.\n");
> +			WARN_ONCE(1, "WARNING: failed to keep up with mmap data.\n"
> +				     "Please try increasing the period (-c) or\n"
> +				     "decreasing the freq (-F) or\n"
> +				     "limiting the number of CPUs");

should suggest -C too

   "limiting the number of CPUs (-C)");


-Andi