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Date: Wed, 31 Oct 2018 16:15:26 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Jiri Olsa <jolsa@...hat.com>, Andi Kleen <ak@...ux.intel.com>,
linux-kernel@...r.kernel.org, leo.yan@...aro.org,
David Miller <davem@...emloft.net>,
Mathieu Poirier <mathieu.poirier@...aro.org>
Subject: Re: [PATCH 4/5] perf intel-pt: Insert callchain context into
synthesized callchains
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@...el.com>
>> Cc: stable@...r.kernel.org # 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
>
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