Commit e48b8311 authored by Kan Liang's avatar Kan Liang Committed by Arnaldo Carvalho de Melo
Browse files

perf machine: Refine the function for LBR call stack reconstruction 



LBR only collect the user call stack. To reconstruct a call stack, both
kernel call stack and user call stack are required. The function
resolve_lbr_callchain_sample() mix the kernel call stack and user call
stack.

Now, with the help of HW idx, perf tool can reconstruct a more complete
call stack by adding some user call stack from previous sample. However,
current implementation is hard to be extended to support it.

Current code path for resolve_lbr_callchain_sample()

  for (j = 0; j < mix_chain_nr; j++) {
       if (ORDER_CALLEE) {
             if (kernel callchain)
                  Fill callchain info
             else if (LBR callchain)
                  Fill callchain info
       } else {
             if (LBR callchain)
                  Fill callchain info
             else if (kernel callchain)
                  Fill callchain info
       }
       add_callchain_ip();
  }

With the patch,

  if (ORDER_CALLEE) {
       for (j = 0; j < NUM of kernel callchain) {
             Fill callchain info
             add_callchain_ip();
       }
       for (; j < mix_chain_nr) {
             Fill callchain info
             add_callchain_ip();
       }
  } else {
       for (; j < NUM of LBR callchain) {
             Fill callchain info
             add_callchain_ip();
       }
       for (j = 0; j < mix_chain_nr) {
             Fill callchain info
             add_callchain_ip();
       }
  }

No functional changes.

Signed-off-by: default avatarKan Liang <kan.liang@linux.intel.com>
Reviewed-by: default avatarAndi Kleen <ak@linux.intel.com>
Acked-by: default avatarJiri Olsa <jolsa@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Pavel Gerasimov <pavel.gerasimov@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Vitaly Slobodskoy <vitaly.slobodskoy@intel.com>
Link: http://lore.kernel.org/lkml/20200319202517.23423-7-kan.liang@linux.intel.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent f8603267

tools/perf/util/machine.c

+76 −35
Original line number Diff line number Diff line
@@ -2214,6 +2214,7 @@ static int resolve_lbr_callchain_sample(struct thread *thread, 
	bool branch;

	struct branch_flags *flags;

	int mix_chain_nr;

	int err;



	for (i = 0; i < chain_nr; i++) {

		if (chain->ips[i] == PERF_CONTEXT_USER)
@@ -2239,50 +2240,90 @@ static int resolve_lbr_callchain_sample(struct thread *thread, 
	 */

	mix_chain_nr = i + 1 + lbr_nr + 1;



	for (j = 0; j < mix_chain_nr; j++) {

		int err;



	if (callchain_param.order == ORDER_CALLEE) {

		/* Add kernel ip */

		for (j = 0; j < i + 1; j++) {

			ip = chain->ips[j];

			branch = false;

			flags = NULL;

			err = add_callchain_ip(thread, cursor, parent,

					       root_al, &cpumode, ip,

					       branch, flags, NULL,

					       branch_from);

			if (err)

				goto error;

		}

		/* Add LBR ip from first entries.to */

		ip = entries[0].to;

		branch = true;

		flags = &entries[0].flags;

		branch_from = entries[0].from;

		err = add_callchain_ip(thread, cursor, parent,

				       root_al, &cpumode, ip,

				       branch, flags, NULL,

				       branch_from);

		if (err)

			goto error;



		if (callchain_param.order == ORDER_CALLEE) {

			if (j < i + 1)

				ip = chain->ips[j];

			else if (j > i + 1) {

		/* Add LBR ip from entries.from one by one. */

		for (j = i + 2; j < mix_chain_nr; j++) {

			k = j - i - 2;

			ip = entries[k].from;

			branch = true;

			flags = &entries[k].flags;

			} else {

				ip = entries[0].to;

				branch = true;

				flags = &entries[0].flags;

				branch_from = entries[0].from;



			err = add_callchain_ip(thread, cursor, parent,

					       root_al, &cpumode, ip,

					       branch, flags, NULL,

					       branch_from);

			if (err)

				goto error;

		}

	} else {

			if (j < lbr_nr) {

		/* Add LBR ip from entries.from one by one. */

		for (j = 0; j < lbr_nr; j++) {

			k = lbr_nr - j - 1;

			ip = entries[k].from;

			branch = true;

			flags = &entries[k].flags;

			} else if (j > lbr_nr)

				ip = chain->ips[i + 1 - (j - lbr_nr)];

			else {



			err = add_callchain_ip(thread, cursor, parent,

					       root_al, &cpumode, ip,

					       branch, flags, NULL,

					       branch_from);

			if (err)

				goto error;

		}



		/* Add LBR ip from first entries.to */

		ip = entries[0].to;

		branch = true;

		flags = &entries[0].flags;

		branch_from = entries[0].from;

			}

		}

		err = add_callchain_ip(thread, cursor, parent,

				       root_al, &cpumode, ip,

				       branch, flags, NULL,

				       branch_from);

		if (err)

			goto error;



		/* Add kernel ip */

		for (j = lbr_nr + 1; j < mix_chain_nr; j++) {

			ip = chain->ips[i + 1 - (j - lbr_nr)];

			branch = false;

			flags = NULL;

			err = add_callchain_ip(thread, cursor, parent,

					       root_al, &cpumode, ip,

					       branch, flags, NULL,

					       branch_from);

			if (err)

			return (err < 0) ? err : 0;

				goto error;

		}

	}

	return 1;



error:

	return (err < 0) ? err : 0;

}



static int find_prev_cpumode(struct ip_callchain *chain, struct thread *thread,

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