perf report: Use properly build_id kernel binaries
Jiri Olsa [Wed, 1 Jun 2011 19:43:46 +0000 (21:43 +0200)]
If we bring the recorded perf data together with kernel binary from another
machine using:

on server A:
perf archive

on server B:
tar xjvf perf.data.tar.bz2 -C ~/.debug

the build_id kernel dso is not properly recognized during the "perf report"
command on server B.

The reason is, that build_id dsos are added during the session initialization,
while the kernel maps are created during the sample event processing.

The machine__create_kernel_maps functions ends up creating new dso object for
kernel, but it does not check if we already have one added by build_id
processing.

Also the build_id reading ABI quirk added in commit:

 - commit b25114817a73bbd2b84ce9dba02ee1ef8989a947
   perf build-id: Add quirk to deal with perf.data file format breakage

populates the "struct build_id_event::pid" with 0, which
is later interpreted as DEFAULT_GUEST_KERNEL_ID.

This is not always correct, so it's better to guess the pid
value based on the "struct build_id_event::header::misc" value.

- Tested with data generated on x86 kernel version v2.6.34
  and reported back on x86_64 current kernel.
- Not tested for guest kernel case.

Note the problem stays for PERF_RECORD_MMAP events recorded by perf that
does not use proper pid (HOST_KERNEL_ID/DEFAULT_GUEST_KERNEL_ID). They are
misinterpreted within the current perf code. Probably there's not much we
can do about that.

Cc: Avi Kivity <avi@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Link: http://lkml.kernel.org/r/20110601194346.GB1934@jolsa.brq.redhat.com
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/header.c
tools/perf/util/symbol.c
tools/perf/util/symbol.h

index d4f3101..b6c1ad1 100644 (file)
@@ -726,7 +726,16 @@ static int perf_header__read_build_ids_abi_quirk(struct perf_header *header,
                        return -1;
 
                bev.header = old_bev.header;
-               bev.pid    = 0;
+
+               /*
+                * As the pid is the missing value, we need to fill
+                * it properly. The header.misc value give us nice hint.
+                */
+               bev.pid = HOST_KERNEL_ID;
+               if (bev.header.misc == PERF_RECORD_MISC_GUEST_USER ||
+                   bev.header.misc == PERF_RECORD_MISC_GUEST_KERNEL)
+                       bev.pid = DEFAULT_GUEST_KERNEL_ID;
+
                memcpy(bev.build_id, old_bev.build_id, sizeof(bev.build_id));
                __event_process_build_id(&bev, filename, session);
 
index a8b5371..e142c21 100644 (file)
@@ -2181,27 +2181,22 @@ size_t machines__fprintf_dsos_buildid(struct rb_root *machines,
        return ret;
 }
 
-struct dso *dso__new_kernel(const char *name)
+static struct dso*
+dso__kernel_findnew(struct machine *machine, const char *name,
+                   const char *short_name, int dso_type)
 {
-       struct dso *dso = dso__new(name ?: "[kernel.kallsyms]");
-
-       if (dso != NULL) {
-               dso__set_short_name(dso, "[kernel]");
-               dso->kernel = DSO_TYPE_KERNEL;
-       }
-
-       return dso;
-}
+       /*
+        * The kernel dso could be created by build_id processing.
+        */
+       struct dso *dso = __dsos__findnew(&machine->kernel_dsos, name);
 
-static struct dso *dso__new_guest_kernel(struct machine *machine,
-                                       const char *name)
-{
-       char bf[PATH_MAX];
-       struct dso *dso = dso__new(name ?: machine__mmap_name(machine, bf,
-                                                             sizeof(bf)));
+       /*
+        * We need to run this in all cases, since during the build_id
+        * processing we had no idea this was the kernel dso.
+        */
        if (dso != NULL) {
-               dso__set_short_name(dso, "[guest.kernel]");
-               dso->kernel = DSO_TYPE_GUEST_KERNEL;
+               dso__set_short_name(dso, short_name);
+               dso->kernel = dso_type;
        }
 
        return dso;
@@ -2219,24 +2214,36 @@ void dso__read_running_kernel_build_id(struct dso *dso, struct machine *machine)
                dso->has_build_id = true;
 }
 
-static struct dso *machine__create_kernel(struct machine *machine)
+static struct dso *machine__get_kernel(struct machine *machine)
 {
        const char *vmlinux_name = NULL;
        struct dso *kernel;
 
        if (machine__is_host(machine)) {
                vmlinux_name = symbol_conf.vmlinux_name;
-               kernel = dso__new_kernel(vmlinux_name);
+               if (!vmlinux_name)
+                       vmlinux_name = "[kernel.kallsyms]";
+
+               kernel = dso__kernel_findnew(machine, vmlinux_name,
+                                            "[kernel]",
+                                            DSO_TYPE_KERNEL);
        } else {
+               char bf[PATH_MAX];
+
                if (machine__is_default_guest(machine))
                        vmlinux_name = symbol_conf.default_guest_vmlinux_name;
-               kernel = dso__new_guest_kernel(machine, vmlinux_name);
+               if (!vmlinux_name)
+                       vmlinux_name = machine__mmap_name(machine, bf,
+                                                         sizeof(bf));
+
+               kernel = dso__kernel_findnew(machine, vmlinux_name,
+                                            "[guest.kernel]",
+                                            DSO_TYPE_GUEST_KERNEL);
        }
 
-       if (kernel != NULL) {
+       if (kernel != NULL && (!kernel->has_build_id))
                dso__read_running_kernel_build_id(kernel, machine);
-               dsos__add(&machine->kernel_dsos, kernel);
-       }
+
        return kernel;
 }
 
@@ -2340,7 +2347,7 @@ void machine__destroy_kernel_maps(struct machine *machine)
 
 int machine__create_kernel_maps(struct machine *machine)
 {
-       struct dso *kernel = machine__create_kernel(machine);
+       struct dso *kernel = machine__get_kernel(machine);
 
        if (kernel == NULL ||
            __machine__create_kernel_maps(machine, kernel) < 0)
index 325ee36..4f377d9 100644 (file)
@@ -155,7 +155,6 @@ struct dso {
 };
 
 struct dso *dso__new(const char *name);
-struct dso *dso__new_kernel(const char *name);
 void dso__delete(struct dso *dso);
 
 int dso__name_len(const struct dso *dso);