Re: [PATCH 4/5] perf intel-pt: Insert callchain context into synthesized callchains

[Adrian Hunter]

On 31/10/18 3:28 PM, Arnaldo Carvalho de Melo wrote:
> Em Wed, Oct 31, 2018 at 11:10:42AM +0200, Adrian Hunter escreveu:
>> In the absence of a fallback, callchains must encode also the callchain
>> context. Do that now there is no fallback.
> 
> So, this one is independent of the first 3 patches, right?

Yes.  I was just going to test it separately when I noticed I had
screwed up my earlier testing.  When I re-tested I discovered this patch
has an off-by-one error:

diff --git a/tools/perf/util/thread-stack.c b/tools/perf/util/thread-stack.c
index afdf36852ac8..61a4286a74dc 100644
--- a/tools/perf/util/thread-stack.c
+++ b/tools/perf/util/thread-stack.c
@@ -337,7 +337,7 @@ void thread_stack__sample(struct thread *thread, struct ip_callchain *chain,
 
 	last_context = context;
 
-	for (i = 2, j = 0; i < sz && j < thread->ts->cnt; i++, j++) {
+	for (i = 2, j = 1; i < sz && j <= thread->ts->cnt; i++, j++) {
 		ip = thread->ts->stack[thread->ts->cnt - j].ret_addr;
 		context = callchain_context(ip, kernel_start);
 		if (context != last_context) {

Shall I send V2?

> So, this one is independent of the first 3 patches, right? Ok, applying
> it first, I'll relook the first ones next.
> 
> - Arnaldo
>  
>> Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
>> Cc: stable@xxxxxxxxxxxxxxx # 4.19
>> ---
>>  tools/perf/util/intel-pt.c     |  6 +++--
>>  tools/perf/util/thread-stack.c | 44 +++++++++++++++++++++++++++-------
>>  tools/perf/util/thread-stack.h |  2 +-
>>  3 files changed, 40 insertions(+), 12 deletions(-)
>>
>> diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
>> index ffa385a029b3..60732213d16a 100644
>> --- a/tools/perf/util/intel-pt.c
>> +++ b/tools/perf/util/intel-pt.c
>> @@ -759,7 +759,8 @@ static struct intel_pt_queue *intel_pt_alloc_queue(struct intel_pt *pt,
>>  	if (pt->synth_opts.callchain) {
>>  		size_t sz = sizeof(struct ip_callchain);
>>  
>> -		sz += pt->synth_opts.callchain_sz * sizeof(u64);
>> +		/* Add 1 to callchain_sz for callchain context */
>> +		sz += (pt->synth_opts.callchain_sz + 1) * sizeof(u64);
>>  		ptq->chain = zalloc(sz);
>>  		if (!ptq->chain)
>>  			goto out_free;
>> @@ -1160,7 +1161,8 @@ static void intel_pt_prep_sample(struct intel_pt *pt,
>>  
>>  	if (pt->synth_opts.callchain) {
>>  		thread_stack__sample(ptq->thread, ptq->chain,
>> -				     pt->synth_opts.callchain_sz, sample->ip);
>> +				     pt->synth_opts.callchain_sz + 1,
>> +				     sample->ip, pt->kernel_start);
>>  		sample->callchain = ptq->chain;
>>  	}
>>  
>> diff --git a/tools/perf/util/thread-stack.c b/tools/perf/util/thread-stack.c
>> index c091635bf7dc..afdf36852ac8 100644
>> --- a/tools/perf/util/thread-stack.c
>> +++ b/tools/perf/util/thread-stack.c
>> @@ -310,20 +310,46 @@ void thread_stack__free(struct thread *thread)
>>  	}
>>  }
>>  
>> +static inline u64 callchain_context(u64 ip, u64 kernel_start)
>> +{
>> +	return ip < kernel_start ? PERF_CONTEXT_USER : PERF_CONTEXT_KERNEL;
>> +}
>> +
>>  void thread_stack__sample(struct thread *thread, struct ip_callchain *chain,
>> -			  size_t sz, u64 ip)
>> +			  size_t sz, u64 ip, u64 kernel_start)
>>  {
>> -	size_t i;
>> +	u64 context = callchain_context(ip, kernel_start);
>> +	u64 last_context;
>> +	size_t i, j;
>>  
>> -	if (!thread || !thread->ts)
>> -		chain->nr = 1;
>> -	else
>> -		chain->nr = min(sz, thread->ts->cnt + 1);
>> +	if (sz < 2) {
>> +		chain->nr = 0;
>> +		return;
>> +	}
>>  
>> -	chain->ips[0] = ip;
>> +	chain->ips[0] = context;
>> +	chain->ips[1] = ip;
>> +
>> +	if (!thread || !thread->ts) {
>> +		chain->nr = 2;
>> +		return;
>> +	}
>> +
>> +	last_context = context;
>> +
>> +	for (i = 2, j = 0; i < sz && j < thread->ts->cnt; i++, j++) {
>> +		ip = thread->ts->stack[thread->ts->cnt - j].ret_addr;
>> +		context = callchain_context(ip, kernel_start);
>> +		if (context != last_context) {
>> +			if (i >= sz - 1)
>> +				break;
>> +			chain->ips[i++] = context;
>> +			last_context = context;
>> +		}
>> +		chain->ips[i] = ip;
>> +	}
>>  
>> -	for (i = 1; i < chain->nr; i++)
>> -		chain->ips[i] = thread->ts->stack[thread->ts->cnt - i].ret_addr;
>> +	chain->nr = i;
>>  }
>>  
>>  struct call_return_processor *
>> diff --git a/tools/perf/util/thread-stack.h b/tools/perf/util/thread-stack.h
>> index b7e41c4ebfdd..f97c00a8c251 100644
>> --- a/tools/perf/util/thread-stack.h
>> +++ b/tools/perf/util/thread-stack.h
>> @@ -84,7 +84,7 @@ int thread_stack__event(struct thread *thread, u32 flags, u64 from_ip,
>>  			u64 to_ip, u16 insn_len, u64 trace_nr);
>>  void thread_stack__set_trace_nr(struct thread *thread, u64 trace_nr);
>>  void thread_stack__sample(struct thread *thread, struct ip_callchain *chain,
>> -			  size_t sz, u64 ip);
>> +			  size_t sz, u64 ip, u64 kernel_start);
>>  int thread_stack__flush(struct thread *thread);
>>  void thread_stack__free(struct thread *thread);
>>  size_t thread_stack__depth(struct thread *thread);
>> -- 
>> 2.17.1
>