Re: [PATCH 1/2] perf pt: Mark PT return events as "return"

[Adrian Hunter]

On 20/05/16 22:52, Andi Kleen wrote:
> From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> 
> With perf script --itrace=cr we can synthesize calls and returns out of
> a PT log. However both calls and returns are marked with the same event,
> called branches. This makes it difficult to read and post process,
> because calls and returns are somewhat diffferent.

Did you consider the sample flags?
e.g.

perf script --itrace=cre -F pid,tid,comm,dso,event,ip,sym,symoff,addr,flags

...
           uname  1807/1807   branches:u:   bB                   0 [unknown] ([unknown]) =>     7fc78a81e18c brk+0xc (/lib/x86_64-linux-gnu/ld-2.19.so)
           uname  1807/1807   branches:u:   br        7fc78a81e1a5 brk+0x25 (/lib/x86_64-linux-gnu/ld-2.19.so) =>     7fc78a81d508 _dl_sysdep_start+0x148 (/lib/x86_64-linux-gnu/ld-2.19.so)
           uname  1807/1807   branches:u:   bc        7fc78a81d630 _dl_sysdep_start+0x270 (/lib/x86_64-linux-gnu/ld-2.19.so) =>     7fc78a81fca0 strlen+0x0 (/lib/x86_64-linux-gnu/ld-2.19.so)
           uname  1807/1807   branches:u:   br        7fc78a81fd88 strlen+0xe8 (/lib/x86_64-linux-gnu/ld-2.19.so) =>     7fc78a81d635 _dl_sysdep_start+0x275 (/lib/x86_64-linux-gnu/ld-2.19.so)
           uname  1807/1807   branches:u:   bc        7fc78a81d52a _dl_sysdep_start+0x16a (/lib/x86_64-linux-gnu/ld-2.19.so) =>     7fc78a81e1e0 sbrk+0x0 (/lib/x86_64-linux-gnu/ld-2.19.so)
           uname  1807/1807   branches:u:   br        7fc78a81e222 sbrk+0x42 (/lib/x86_64-linux-gnu/ld-2.19.so) =>     7fc78a81d52f _dl_sysdep_start+0x16f (/lib/x86_64-linux-gnu/ld-2.19.so)
           uname  1807/1807   branches:u:   bc        7fc78a81d563 _dl_sysdep_start+0x1a3 (/lib/x86_64-linux-gnu/ld-2.19.so) =>     7fc78a807910 dl_main+0x0 (/lib/x86_64-linux-gnu/ld-2.19.so)
           uname  1807/1807   branches:u:   bE        7fc78a807929 dl_main+0x19 (/lib/x86_64-linux-gnu/ld-2.19.so) =>                0 [unknown] ([unknown])
...

You can see 'c' and 'r' flags for calls and returns.

> 
> Create a separate return event and mark the returns as return.
> 
> Cc: adrian.hunter@xxxxxxxxx
> Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> ---
>  tools/perf/util/intel-pt.c | 53 +++++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 48 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
> index ddec87f6e616..25f839e765ef 100644
> --- a/tools/perf/util/intel-pt.c
> +++ b/tools/perf/util/intel-pt.c
> @@ -82,9 +82,12 @@ struct intel_pt {
>  	u64 instructions_id;
>  
>  	bool sample_branches;
> +	bool sample_returns;
>  	u32 branches_filter;
>  	u64 branches_sample_type;
> +	u64 returns_sample_type;
>  	u64 branches_id;
> +	u64 returns_id;
>  
>  	bool sample_transactions;
>  	u64 transactions_sample_type;
> @@ -960,7 +963,8 @@ static int intel_pt_inject_event(union perf_event *event,
>  	return perf_event__synthesize_sample(event, type, 0, sample, swapped);
>  }
>  
> -static int intel_pt_synth_branch_sample(struct intel_pt_queue *ptq)
> +static int intel_pt_synth_branch_sample(struct intel_pt_queue *ptq,
> +					bool is_return)
>  {
>  	int ret;
>  	struct intel_pt *pt = ptq->pt;
> @@ -990,8 +994,13 @@ static int intel_pt_synth_branch_sample(struct intel_pt_queue *ptq)
>  	sample.pid = ptq->pid;
>  	sample.tid = ptq->tid;
>  	sample.addr = ptq->state->to_ip;
> -	sample.id = ptq->pt->branches_id;
> -	sample.stream_id = ptq->pt->branches_id;
> +	if (is_return) {
> +		sample.id = ptq->pt->returns_id;
> +		sample.stream_id = ptq->pt->returns_id;
> +	} else {
> +		sample.id = ptq->pt->branches_id;
> +		sample.stream_id = ptq->pt->branches_id;
> +	}
>  	sample.period = 1;
>  	sample.cpu = ptq->cpu;
>  	sample.flags = ptq->flags;
> @@ -1014,6 +1023,8 @@ static int intel_pt_synth_branch_sample(struct intel_pt_queue *ptq)
>  
>  	if (pt->synth_opts.inject) {
>  		ret = intel_pt_inject_event(event, &sample,
> +					    is_return ?
> +					    pt->returns_sample_type :
>  					    pt->branches_sample_type,
>  					    pt->synth_needs_swap);
>  		if (ret)
> @@ -1241,7 +1252,13 @@ static int intel_pt_sample(struct intel_pt_queue *ptq)
>  		thread_stack__set_trace_nr(ptq->thread, state->trace_nr);
>  
>  	if (pt->sample_branches) {
> -		err = intel_pt_synth_branch_sample(ptq);
> +		err = intel_pt_synth_branch_sample(ptq, false);
> +		if (err)
> +			return err;
> +	}
> +
> +	if (pt->sample_returns) {
> +		err = intel_pt_synth_branch_sample(ptq, true);
>  		if (err)
>  			return err;
>  	}
> @@ -1956,7 +1973,33 @@ static int intel_pt_synth_events(struct intel_pt *pt,
>  		}
>  		pt->sample_branches = true;
>  		pt->branches_sample_type = attr.sample_type;
> -		pt->branches_id = id;
> +		pt->branches_id = id++;
> +	}
> +	if (pt->synth_opts.returns) {
> +		attr.config = PERF_COUNT_HW_BRANCH_INSTRUCTIONS;
> +		attr.sample_period = 1;
> +		attr.sample_type |= PERF_SAMPLE_ADDR;
> +		attr.sample_type &= ~(u64)PERF_SAMPLE_CALLCHAIN;
> +		attr.sample_type &= ~(u64)PERF_SAMPLE_BRANCH_STACK;
> +		pr_debug("Synthesizing 'return' event with id %" PRIu64 " sample type %#" PRIx64 "\n",
> +			 id, (u64)attr.sample_type);
> +		err = intel_pt_synth_event(session, &attr, id);
> +		if (err) {
> +			pr_err("%s: failed to synthesize 'return' event type\n",
> +			       __func__);
> +			return err;
> +		}
> +		pt->sample_returns = true;
> +		pt->returns_sample_type = attr.sample_type;
> +		pt->returns_id = id;
> +		evlist__for_each(evlist, evsel) {
> +			if (evsel->id && evsel->id[0] == pt->returns_id) {
> +				if (evsel->name)
> +					zfree(&evsel->name);
> +				evsel->name = strdup("return");
> +				break;
> +			}
> +		}
>  	}
>  
>  	pt->synth_needs_swap = evsel->needs_swap;
>