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

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Wed, Oct 31, 2018 at 04:20:45PM +0200, Adrian Hunter escreveu:
> On 31/10/18 4:15 PM, Adrian Hunter wrote:
> > 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?
> 
> I have attached it

Thanks!

> >From 19a9fbdbd3729c7f14c9c1f0ac79c18cce91ff60 Mon Sep 17 00:00:00 2001
> From: Adrian Hunter <adrian.hunter@intel.com>
> Date: Wed, 31 Oct 2018 09:31:25 +0200
> Subject: [PATCH V2 4/5] perf intel-pt: Insert callchain context into
>  synthesized callchains
> 
> In the absence of a fallback, callchains must encode also the callchain
> context. Do that now there is no fallback.
> 
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> Cc: stable@vger.kernel.org # 4.19
> ---
> 
> 
> Changes in V2:
> 
> 	Fix off-by-one error
> 
> 
>  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..61a4286a74dc 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 = 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) {
> +			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
>