linux-kernel - Re: [PATCH 0/4] perf, pt, coresight: AUX flags and VMX update

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Date:   Mon, 20 Feb 2017 17:39:43 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...radead.org>
Cc:     linux-kernel@...r.kernel.org, vince@...ter.net, eranian@...gle.com,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH 0/4] perf, pt, coresight: AUX flags and VMX update

On 20/02/17 17:18, Alexander Shishkin wrote:
> Alexander Shishkin <alexander.shishkin@...ux.intel.com> writes:
> 
>> With the vmm_exclusive=0, PT seems to be much more usable on BDW now. This
>> patchset does three things:
>>  * adds a flag to PERF_RECORD_AUX, signalling that a transaction has gaps
>>    in it (due to VMX root mode kicking in),
> 
> Hi Arnaldo & Adrian,
> 
> In the above context, will something like this be fine?

Looks fine to me.

Acked-by: Adrian Hunter <adrian.hunter@...el.com>


> 
> Regards,
> --
> Alex
> 
>>>From 5aba03e79c1119408b44435af8c4cee2480b0775 Mon Sep 17 00:00:00 2001
> From: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Date: Mon, 20 Feb 2017 17:08:53 +0200
> Subject: [PATCH] perf tools: Handle partial AUX records and print a warning
> 
> This patch decodes the 'partial' flag in AUX records and prints
> a warning to the user, so that they don't have to guess why their
> PT traces contain gaps (or missing altogether):
> 
>> Warning:
>> AUX data had gaps in it 6 times out of 8!
>>
>> Are you running a KVM guest in the background?
> 
> Currently this is the only reason for partial records.
> 
> Cc: Adrian Hunter <adrian.hunter@...el.com>
> Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> ---
>  tools/include/uapi/linux/perf_event.h |  1 +
>  tools/perf/util/event.c               |  5 +++--
>  tools/perf/util/event.h               |  1 +
>  tools/perf/util/session.c             | 17 ++++++++++++++---
>  4 files changed, 19 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
> index c66a485a24..8306415207 100644
> --- a/tools/include/uapi/linux/perf_event.h
> +++ b/tools/include/uapi/linux/perf_event.h
> @@ -885,6 +885,7 @@ enum perf_callchain_context {
>   */
>  #define PERF_AUX_FLAG_TRUNCATED		0x01	/* record was truncated to fit */
>  #define PERF_AUX_FLAG_OVERWRITE		0x02	/* snapshot from overwrite mode */
> +#define PERF_AUX_FLAG_PARTIAL		0x04	/* record contains gaps */
>  
>  #define PERF_FLAG_FD_NO_GROUP		(1UL << 0)
>  #define PERF_FLAG_FD_OUTPUT		(1UL << 1)
> diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
> index 4ea7ce72ed..ba193cd019 100644
> --- a/tools/perf/util/event.c
> +++ b/tools/perf/util/event.c
> @@ -1153,11 +1153,12 @@ int perf_event__process_exit(struct perf_tool *tool __maybe_unused,
>  
>  size_t perf_event__fprintf_aux(union perf_event *event, FILE *fp)
>  {
> -	return fprintf(fp, " offset: %#"PRIx64" size: %#"PRIx64" flags: %#"PRIx64" [%s%s]\n",
> +	return fprintf(fp, " offset: %#"PRIx64" size: %#"PRIx64" flags: %#"PRIx64" [%s%s%s]\n",
>  		       event->aux.aux_offset, event->aux.aux_size,
>  		       event->aux.flags,
>  		       event->aux.flags & PERF_AUX_FLAG_TRUNCATED ? "T" : "",
> -		       event->aux.flags & PERF_AUX_FLAG_OVERWRITE ? "O" : "");
> +		       event->aux.flags & PERF_AUX_FLAG_OVERWRITE ? "O" : "",
> +		       event->aux.flags & PERF_AUX_FLAG_PARTIAL   ? "P" : "");
>  }
>  
>  size_t perf_event__fprintf_itrace_start(union perf_event *event, FILE *fp)
> diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
> index c735c53a26..d7e53fe176 100644
> --- a/tools/perf/util/event.h
> +++ b/tools/perf/util/event.h
> @@ -269,6 +269,7 @@ struct events_stats {
>  	u64 total_lost;
>  	u64 total_lost_samples;
>  	u64 total_aux_lost;
> +	u64 total_aux_partial;
>  	u64 total_invalid_chains;
>  	u32 nr_events[PERF_RECORD_HEADER_MAX];
>  	u32 nr_non_filtered_samples;
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index 4cdbc8f5f1..abdb797fa4 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -1258,9 +1258,12 @@ static int machines__deliver_event(struct machines *machines,
>  	case PERF_RECORD_UNTHROTTLE:
>  		return tool->unthrottle(tool, event, sample, machine);
>  	case PERF_RECORD_AUX:
> -		if (tool->aux == perf_event__process_aux &&
> -		    (event->aux.flags & PERF_AUX_FLAG_TRUNCATED))
> -			evlist->stats.total_aux_lost += 1;
> +		if (tool->aux == perf_event__process_aux) {
> +			if (event->aux.flags & PERF_AUX_FLAG_TRUNCATED)
> +				evlist->stats.total_aux_lost += 1;
> +			if (event->aux.flags & PERF_AUX_FLAG_PARTIAL)
> +				evlist->stats.total_aux_partial += 1;
> +		}
>  		return tool->aux(tool, event, sample, machine);
>  	case PERF_RECORD_ITRACE_START:
>  		return tool->itrace_start(tool, event, sample, machine);
> @@ -1548,6 +1551,14 @@ static void perf_session__warn_about_errors(const struct perf_session *session)
>  			    stats->nr_events[PERF_RECORD_AUX]);
>  	}
>  
> +	if (session->tool->aux == perf_event__process_aux &&
> +	    stats->total_aux_partial != 0) {
> +		ui__warning("AUX data had gaps in it %" PRIu64 " times out of %u!\n\n"
> +		            "Are you running a KVM guest in the background?\n\n",
> +			    stats->total_aux_partial,
> +			    stats->nr_events[PERF_RECORD_AUX]);
> +	}
> +
>  	if (stats->nr_unknown_events != 0) {
>  		ui__warning("Found %u unknown events!\n\n"
>  			    "Is this an older tool processing a perf.data "
>