Re: [PATCH v7 4/8] perf tool: synthesize namespace events for current processes

[Hari Bathini]

On Thursday 02 March 2017 02:35 AM, Arnaldo Carvalho de Melo wrote:
> Em Tue, Feb 21, 2017 at 07:31:44PM +0530, Hari Bathini escreveu:
> > Synthesize PERF_RECORD_NAMESPACES events for processes that were
> > running prior to invocation of perf record, the data for which is
> > taken from /proc/$PID/ns. These changes make way for analyzing
> > events with regard to namespaces.
> >
> > Signed-off-by: Hari Bathini <hbathini@xxxxxxxxxxxxxxxxxx>
> > ---
> >   tools/perf/builtin-record.c |   27 +++++++++--
> >   tools/perf/util/event.c     |  107 +++++++++++++++++++++++++++++++++++++++++--
> >   tools/perf/util/event.h     |    6 ++
> >   3 files changed, 130 insertions(+), 10 deletions(-)
> >
> > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> > index a8b9a78..f4bf6a6 100644
> > --- a/tools/perf/builtin-record.c
> > +++ b/tools/perf/builtin-record.c
> > @@ -986,6 +986,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
> >   	 */
> >   	if (forks) {
> >   		union perf_event *event;
> > +		pid_t tgid;
> >   
> >   		event = malloc(sizeof(event->comm) + machine->id_hdr_size);
> >   		if (event == NULL) {
> > @@ -999,10 +1000,28 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
> >   		 * cannot see a correct process name for those events.
> >   		 * Synthesize COMM event to prevent it.
> >   		 */
> > -		perf_event__synthesize_comm(tool, event,
> > -					    rec->evlist->workload.pid,
> > -					    process_synthesized_event,
> > -					    machine);
> > +		tgid = perf_event__synthesize_comm(tool, event,
> > +						   rec->evlist->workload.pid,
> > +						   process_synthesized_event,
> > +						   machine);
> > +		free(event);
> > +
> > +		if (tgid == -1)
> > +			goto out_child;
> > +
> > +		event = malloc(sizeof(event->namespaces) + machine->id_hdr_size);
> > +		if (event == NULL) {
> > +			err = -ENOMEM;
> > +			goto out_child;
> > +		}
> > +
> > +		/*
> > +		 * Synthesize NAMESPACES event for the command specified.
> > +		 */
> > +		perf_event__synthesize_namespaces(tool, event,
> > +						  rec->evlist->workload.pid,
> > +						  tgid, process_synthesized_event,
> > +						  machine);
> >   		free(event);
> >   
> >   		perf_evlist__start_workload(rec->evlist);
> > diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
> > index f118eac..c8c112a 100644
> > --- a/tools/perf/util/event.c
> > +++ b/tools/perf/util/event.c
> > @@ -50,6 +50,16 @@ static const char *perf_event__names[] = {
> >   	[PERF_RECORD_TIME_CONV]			= "TIME_CONV",
> >   };
> >   
> > +static const char *perf_ns__names[] = {
> > +	[NET_NS_INDEX]		= "net",
> > +	[UTS_NS_INDEX]		= "uts",
> > +	[IPC_NS_INDEX]		= "ipc",
> > +	[PID_NS_INDEX]		= "pid",
> > +	[USER_NS_INDEX]		= "user",
> > +	[MNT_NS_INDEX]		= "mnt",
> > +	[CGROUP_NS_INDEX]	= "cgroup",
> > +};
> > +
> >   const char *perf_event__name(unsigned int id)
> >   {
> >   	if (id >= ARRAY_SIZE(perf_event__names))
> > @@ -59,6 +69,13 @@ const char *perf_event__name(unsigned int id)
> >   	return perf_event__names[id];
> >   }
> >   
> > +static const char *perf_ns__name(unsigned int id)
> > +{
> > +	if (id >= ARRAY_SIZE(perf_ns__names))
> > +		return "UNKNOWN";
> > +	return perf_ns__names[id];
> > +}
> > +
> >   static int perf_tool__process_synth_event(struct perf_tool *tool,
> >   					  union perf_event *event,
> >   					  struct machine *machine,
> > @@ -204,6 +221,56 @@ pid_t perf_event__synthesize_comm(struct perf_tool *tool,
> >   	return tgid;
> >   }
> >   
> > +static void perf_event__get_ns_link_info(pid_t pid, const char *ns,
> > +					 struct perf_ns_link_info *ns_link_info)
> > +{
> > +	struct stat64 st;
> > +	char proc_ns[128];
> > +
> > +	sprintf(proc_ns, "/proc/%u/ns/%s", pid, ns);
> > +	if (stat64(proc_ns, &st) == 0) {
> > +		ns_link_info->dev = st.st_dev;
> > +		ns_link_info->ino = st.st_ino;
> > +	}
> > +}
> > +
> > +int perf_event__synthesize_namespaces(struct perf_tool *tool,
> > +				      union perf_event *event,
> > +				      pid_t pid, pid_t tgid,
> > +				      perf_event__handler_t process,
> > +				      struct machine *machine)
> > +{
> > +	u32 idx;
> > +	struct perf_ns_link_info *ns_link_info;
> > +
> > +	if (!tool->namespace_events)
> > +		return 0;
> > +
> > +	memset(&event->namespaces, 0,
> > +	       sizeof(event->namespaces) + machine->id_hdr_size);
> > +
> > +	event->namespaces.pid = tgid;
> > +	event->namespaces.tid = pid;
> > +
> > +	event->namespaces.nr_namespaces = NR_NAMESPACES;
> Huh? Don't you have to first figure out how many namespaces a process is
> in to then set this field?

NR_NAMESPACES is the total number of namespaces. For synthesized namespace
events, data is obtained from /proc/<pid>/ns/ dir. Looking at this dir, it
is difficult to arrive at the total number of namespaces in kernel, as
some namespaces can be compiled in/out of the kernel. NR_NAMESPACES is
used instead. Its value is most likely the same for kernel and perf tool
unless a new namespace is introduced - the warning in previous patch is
intended to alert the user about such scenario.

Thanks
Hari