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* [PATCH] perf: Don't clone maps from parent when synthesizing forks
@ 2018-10-31  5:24 David Miller
  2018-10-31 13:00 ` Arnaldo Carvalho de Melo
                   ` (2 more replies)
  0 siblings, 3 replies; 5+ messages in thread
From: David Miller @ 2018-10-31  5:24 UTC (permalink / raw)
  To: acme; +Cc: linux-kernel, jolsa


When synthesizing FORK events, we are trying to create thread objects
for the already running tasks on the machine.

Normally, for a kernel FORK event, we want to clone the parent's maps
because that is what the kernel just did.

But when synthesizing, this should not be done.  If we do, we end up
with overlapping maps as we process the sythesized MMAP2 events that
get delivered shortly thereafter.

Use the FORK event misc flags in an internal way to signal this
situation, so we can elide the map clone when appropriate.

Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index f35eb72739c0..9de8780ac8d9 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -646,10 +646,12 @@ struct perf_event_mmap_page {
  *
  *   PERF_RECORD_MISC_MMAP_DATA  - PERF_RECORD_MMAP* events
  *   PERF_RECORD_MISC_COMM_EXEC  - PERF_RECORD_COMM event
+ *   PERF_RECORD_MISC_FORK_EXEC  - PERF_RECORD_FORK event (perf internal)
  *   PERF_RECORD_MISC_SWITCH_OUT - PERF_RECORD_SWITCH* events
  */
 #define PERF_RECORD_MISC_MMAP_DATA		(1 << 13)
 #define PERF_RECORD_MISC_COMM_EXEC		(1 << 13)
+#define PERF_RECORD_MISC_FORK_EXEC		(1 << 13)
 #define PERF_RECORD_MISC_SWITCH_OUT		(1 << 13)
 /*
  * These PERF_RECORD_MISC_* flags below are safely reused
diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
index f35eb72739c0..9de8780ac8d9 100644
--- a/tools/include/uapi/linux/perf_event.h
+++ b/tools/include/uapi/linux/perf_event.h
@@ -646,10 +646,12 @@ struct perf_event_mmap_page {
  *
  *   PERF_RECORD_MISC_MMAP_DATA  - PERF_RECORD_MMAP* events
  *   PERF_RECORD_MISC_COMM_EXEC  - PERF_RECORD_COMM event
+ *   PERF_RECORD_MISC_FORK_EXEC  - PERF_RECORD_FORK event (perf internal)
  *   PERF_RECORD_MISC_SWITCH_OUT - PERF_RECORD_SWITCH* events
  */
 #define PERF_RECORD_MISC_MMAP_DATA		(1 << 13)
 #define PERF_RECORD_MISC_COMM_EXEC		(1 << 13)
+#define PERF_RECORD_MISC_FORK_EXEC		(1 << 13)
 #define PERF_RECORD_MISC_SWITCH_OUT		(1 << 13)
 /*
  * These PERF_RECORD_MISC_* flags below are safely reused
diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index bc646185f8d9..e9c108a6b1c3 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -308,6 +308,7 @@ static int perf_event__synthesize_fork(struct perf_tool *tool,
 	event->fork.pid  = tgid;
 	event->fork.tid  = pid;
 	event->fork.header.type = PERF_RECORD_FORK;
+	event->fork.header.misc = PERF_RECORD_MISC_FORK_EXEC;
 
 	event->fork.header.size = (sizeof(event->fork) + machine->id_hdr_size);
 
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 111ae858cbcb..214b7979c4e7 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1708,6 +1708,7 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event
 	struct thread *parent = machine__findnew_thread(machine,
 							event->fork.ppid,
 							event->fork.ptid);
+	bool do_maps_clone = true;
 	int err = 0;
 
 	if (dump_trace)
@@ -1737,8 +1738,11 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event
 	thread = machine__findnew_thread(machine, event->fork.pid,
 					 event->fork.tid);
 
+	if (event->fork.header.misc & PERF_RECORD_MISC_FORK_EXEC)
+		do_maps_clone = false;
+
 	if (thread == NULL || parent == NULL ||
-	    thread__fork(thread, parent, sample->time) < 0) {
+	    thread__fork(thread, parent, sample->time, do_maps_clone) < 0) {
 		dump_printf("problem processing PERF_RECORD_FORK, skipping event.\n");
 		err = -1;
 	}
diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index 2048d393ece6..54b2c9ceba9f 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -330,7 +330,8 @@ static int thread__prepare_access(struct thread *thread)
 }
 
 static int thread__clone_map_groups(struct thread *thread,
-				    struct thread *parent)
+				    struct thread *parent,
+				    bool do_maps_clone)
 {
 	/* This is new thread, we share map groups for process. */
 	if (thread->pid_ == parent->pid_)
@@ -341,15 +342,14 @@ static int thread__clone_map_groups(struct thread *thread,
 			 thread->pid_, thread->tid, parent->pid_, parent->tid);
 		return 0;
 	}
-
 	/* But this one is new process, copy maps. */
-	if (map_groups__clone(thread, parent->mg) < 0)
+	if (do_maps_clone &&
+	    map_groups__clone(thread, parent->mg) < 0)
 		return -ENOMEM;
-
 	return 0;
 }
 
-int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp)
+int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp, bool do_maps_clone)
 {
 	if (parent->comm_set) {
 		const char *comm = thread__comm_str(parent);
@@ -362,7 +362,7 @@ int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp)
 	}
 
 	thread->ppid = parent->tid;
-	return thread__clone_map_groups(thread, parent);
+	return thread__clone_map_groups(thread, parent, do_maps_clone);
 }
 
 void thread__find_cpumode_addr_location(struct thread *thread, u64 addr,
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index 07606aa6998d..7e30fe99b74b 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -87,7 +87,7 @@ struct comm *thread__comm(const struct thread *thread);
 struct comm *thread__exec_comm(const struct thread *thread);
 const char *thread__comm_str(const struct thread *thread);
 int thread__insert_map(struct thread *thread, struct map *map);
-int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp);
+int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp, bool do_maps_clone);
 size_t thread__fprintf(struct thread *thread, FILE *fp);
 
 struct thread *thread__main_thread(struct machine *machine, struct thread *thread);

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] perf: Don't clone maps from parent when synthesizing forks
  2018-10-31  5:24 [PATCH] perf: Don't clone maps from parent when synthesizing forks David Miller
@ 2018-10-31 13:00 ` Arnaldo Carvalho de Melo
  2018-10-31 13:01 ` Jiri Olsa
  2018-10-31 22:12 ` [tip:perf/urgent] perf tools: " tip-bot for David Miller
  2 siblings, 0 replies; 5+ messages in thread
From: Arnaldo Carvalho de Melo @ 2018-10-31 13:00 UTC (permalink / raw)
  To: David Miller; +Cc: linux-kernel, jolsa, Namhyung Kim

Em Tue, Oct 30, 2018 at 10:24:04PM -0700, David Miller escreveu:
> 
> When synthesizing FORK events, we are trying to create thread objects
> for the already running tasks on the machine.
> 
> Normally, for a kernel FORK event, we want to clone the parent's maps
> because that is what the kernel just did.
> 
> But when synthesizing, this should not be done.  If we do, we end up
> with overlapping maps as we process the sythesized MMAP2 events that
> get delivered shortly thereafter.
> 
> Use the FORK event misc flags in an internal way to signal this
> situation, so we can elide the map clone when appropriate.

Thanks, applied.

- Arnaldo
 
> Signed-off-by: David S. Miller <davem@davemloft.net>
> 
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index f35eb72739c0..9de8780ac8d9 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -646,10 +646,12 @@ struct perf_event_mmap_page {
>   *
>   *   PERF_RECORD_MISC_MMAP_DATA  - PERF_RECORD_MMAP* events
>   *   PERF_RECORD_MISC_COMM_EXEC  - PERF_RECORD_COMM event
> + *   PERF_RECORD_MISC_FORK_EXEC  - PERF_RECORD_FORK event (perf internal)
>   *   PERF_RECORD_MISC_SWITCH_OUT - PERF_RECORD_SWITCH* events
>   */
>  #define PERF_RECORD_MISC_MMAP_DATA		(1 << 13)
>  #define PERF_RECORD_MISC_COMM_EXEC		(1 << 13)
> +#define PERF_RECORD_MISC_FORK_EXEC		(1 << 13)
>  #define PERF_RECORD_MISC_SWITCH_OUT		(1 << 13)
>  /*
>   * These PERF_RECORD_MISC_* flags below are safely reused
> diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
> index f35eb72739c0..9de8780ac8d9 100644
> --- a/tools/include/uapi/linux/perf_event.h
> +++ b/tools/include/uapi/linux/perf_event.h
> @@ -646,10 +646,12 @@ struct perf_event_mmap_page {
>   *
>   *   PERF_RECORD_MISC_MMAP_DATA  - PERF_RECORD_MMAP* events
>   *   PERF_RECORD_MISC_COMM_EXEC  - PERF_RECORD_COMM event
> + *   PERF_RECORD_MISC_FORK_EXEC  - PERF_RECORD_FORK event (perf internal)
>   *   PERF_RECORD_MISC_SWITCH_OUT - PERF_RECORD_SWITCH* events
>   */
>  #define PERF_RECORD_MISC_MMAP_DATA		(1 << 13)
>  #define PERF_RECORD_MISC_COMM_EXEC		(1 << 13)
> +#define PERF_RECORD_MISC_FORK_EXEC		(1 << 13)
>  #define PERF_RECORD_MISC_SWITCH_OUT		(1 << 13)
>  /*
>   * These PERF_RECORD_MISC_* flags below are safely reused
> diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
> index bc646185f8d9..e9c108a6b1c3 100644
> --- a/tools/perf/util/event.c
> +++ b/tools/perf/util/event.c
> @@ -308,6 +308,7 @@ static int perf_event__synthesize_fork(struct perf_tool *tool,
>  	event->fork.pid  = tgid;
>  	event->fork.tid  = pid;
>  	event->fork.header.type = PERF_RECORD_FORK;
> +	event->fork.header.misc = PERF_RECORD_MISC_FORK_EXEC;
>  
>  	event->fork.header.size = (sizeof(event->fork) + machine->id_hdr_size);
>  
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 111ae858cbcb..214b7979c4e7 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -1708,6 +1708,7 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event
>  	struct thread *parent = machine__findnew_thread(machine,
>  							event->fork.ppid,
>  							event->fork.ptid);
> +	bool do_maps_clone = true;
>  	int err = 0;
>  
>  	if (dump_trace)
> @@ -1737,8 +1738,11 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event
>  	thread = machine__findnew_thread(machine, event->fork.pid,
>  					 event->fork.tid);
>  
> +	if (event->fork.header.misc & PERF_RECORD_MISC_FORK_EXEC)
> +		do_maps_clone = false;
> +
>  	if (thread == NULL || parent == NULL ||
> -	    thread__fork(thread, parent, sample->time) < 0) {
> +	    thread__fork(thread, parent, sample->time, do_maps_clone) < 0) {
>  		dump_printf("problem processing PERF_RECORD_FORK, skipping event.\n");
>  		err = -1;
>  	}
> diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
> index 2048d393ece6..54b2c9ceba9f 100644
> --- a/tools/perf/util/thread.c
> +++ b/tools/perf/util/thread.c
> @@ -330,7 +330,8 @@ static int thread__prepare_access(struct thread *thread)
>  }
>  
>  static int thread__clone_map_groups(struct thread *thread,
> -				    struct thread *parent)
> +				    struct thread *parent,
> +				    bool do_maps_clone)
>  {
>  	/* This is new thread, we share map groups for process. */
>  	if (thread->pid_ == parent->pid_)
> @@ -341,15 +342,14 @@ static int thread__clone_map_groups(struct thread *thread,
>  			 thread->pid_, thread->tid, parent->pid_, parent->tid);
>  		return 0;
>  	}
> -
>  	/* But this one is new process, copy maps. */
> -	if (map_groups__clone(thread, parent->mg) < 0)
> +	if (do_maps_clone &&
> +	    map_groups__clone(thread, parent->mg) < 0)
>  		return -ENOMEM;
> -
>  	return 0;
>  }
>  
> -int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp)
> +int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp, bool do_maps_clone)
>  {
>  	if (parent->comm_set) {
>  		const char *comm = thread__comm_str(parent);
> @@ -362,7 +362,7 @@ int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp)
>  	}
>  
>  	thread->ppid = parent->tid;
> -	return thread__clone_map_groups(thread, parent);
> +	return thread__clone_map_groups(thread, parent, do_maps_clone);
>  }
>  
>  void thread__find_cpumode_addr_location(struct thread *thread, u64 addr,
> diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
> index 07606aa6998d..7e30fe99b74b 100644
> --- a/tools/perf/util/thread.h
> +++ b/tools/perf/util/thread.h
> @@ -87,7 +87,7 @@ struct comm *thread__comm(const struct thread *thread);
>  struct comm *thread__exec_comm(const struct thread *thread);
>  const char *thread__comm_str(const struct thread *thread);
>  int thread__insert_map(struct thread *thread, struct map *map);
> -int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp);
> +int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp, bool do_maps_clone);
>  size_t thread__fprintf(struct thread *thread, FILE *fp);
>  
>  struct thread *thread__main_thread(struct machine *machine, struct thread *thread);

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] perf: Don't clone maps from parent when synthesizing forks
  2018-10-31  5:24 [PATCH] perf: Don't clone maps from parent when synthesizing forks David Miller
  2018-10-31 13:00 ` Arnaldo Carvalho de Melo
@ 2018-10-31 13:01 ` Jiri Olsa
  2018-10-31 13:06   ` Arnaldo Carvalho de Melo
  2018-10-31 22:12 ` [tip:perf/urgent] perf tools: " tip-bot for David Miller
  2 siblings, 1 reply; 5+ messages in thread
From: Jiri Olsa @ 2018-10-31 13:01 UTC (permalink / raw)
  To: David Miller; +Cc: acme, linux-kernel

On Tue, Oct 30, 2018 at 10:24:04PM -0700, David Miller wrote:

SNIP

> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 111ae858cbcb..214b7979c4e7 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -1708,6 +1708,7 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event
>  	struct thread *parent = machine__findnew_thread(machine,
>  							event->fork.ppid,
>  							event->fork.ptid);
> +	bool do_maps_clone = true;
>  	int err = 0;
>  
>  	if (dump_trace)
> @@ -1737,8 +1738,11 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event
>  	thread = machine__findnew_thread(machine, event->fork.pid,
>  					 event->fork.tid);
>  
> +	if (event->fork.header.misc & PERF_RECORD_MISC_FORK_EXEC)
> +		do_maps_clone = false;

could you please put some comment in here shortly
explaining the reason behind this flag

> +
>  	if (thread == NULL || parent == NULL ||
> -	    thread__fork(thread, parent, sample->time) < 0) {
> +	    thread__fork(thread, parent, sample->time, do_maps_clone) < 0) {
>  		dump_printf("problem processing PERF_RECORD_FORK, skipping event.\n");
>  		err = -1;
>  	}
> diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
> index 2048d393ece6..54b2c9ceba9f 100644
> --- a/tools/perf/util/thread.c
> +++ b/tools/perf/util/thread.c
> @@ -330,7 +330,8 @@ static int thread__prepare_access(struct thread *thread)
>  }
>  
>  static int thread__clone_map_groups(struct thread *thread,
> -				    struct thread *parent)
> +				    struct thread *parent,
> +				    bool do_maps_clone)
>  {
>  	/* This is new thread, we share map groups for process. */
>  	if (thread->pid_ == parent->pid_)
> @@ -341,15 +342,14 @@ static int thread__clone_map_groups(struct thread *thread,
>  			 thread->pid_, thread->tid, parent->pid_, parent->tid);
>  		return 0;
>  	}
> -
>  	/* But this one is new process, copy maps. */
> -	if (map_groups__clone(thread, parent->mg) < 0)
> +	if (do_maps_clone &&
> +	    map_groups__clone(thread, parent->mg) < 0)
>  		return -ENOMEM;
> -
>  	return 0;

we could move all this into one line:

	return do_maps_clone ? map_groups__clone(thread, parent->mg) : 0;

thanks,
jirka

>  }
>  
> -int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp)
> +int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp, bool do_maps_clone)
>  {
>  	if (parent->comm_set) {
>  		const char *comm = thread__comm_str(parent);
> @@ -362,7 +362,7 @@ int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp)
>  	}
>  
>  	thread->ppid = parent->tid;
> -	return thread__clone_map_groups(thread, parent);
> +	return thread__clone_map_groups(thread, parent, do_maps_clone);
>  }
>  
>  void thread__find_cpumode_addr_location(struct thread *thread, u64 addr,
> diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
> index 07606aa6998d..7e30fe99b74b 100644
> --- a/tools/perf/util/thread.h
> +++ b/tools/perf/util/thread.h
> @@ -87,7 +87,7 @@ struct comm *thread__comm(const struct thread *thread);
>  struct comm *thread__exec_comm(const struct thread *thread);
>  const char *thread__comm_str(const struct thread *thread);
>  int thread__insert_map(struct thread *thread, struct map *map);
> -int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp);
> +int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp, bool do_maps_clone);
>  size_t thread__fprintf(struct thread *thread, FILE *fp);
>  
>  struct thread *thread__main_thread(struct machine *machine, struct thread *thread);

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] perf: Don't clone maps from parent when synthesizing forks
  2018-10-31 13:01 ` Jiri Olsa
@ 2018-10-31 13:06   ` Arnaldo Carvalho de Melo
  0 siblings, 0 replies; 5+ messages in thread
From: Arnaldo Carvalho de Melo @ 2018-10-31 13:06 UTC (permalink / raw)
  To: Jiri Olsa; +Cc: David Miller, linux-kernel

Em Wed, Oct 31, 2018 at 02:01:38PM +0100, Jiri Olsa escreveu:
> On Tue, Oct 30, 2018 at 10:24:04PM -0700, David Miller wrote:
> 
> SNIP
> 
> > diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> > index 111ae858cbcb..214b7979c4e7 100644
> > --- a/tools/perf/util/machine.c
> > +++ b/tools/perf/util/machine.c
> > @@ -1708,6 +1708,7 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event
> >  	struct thread *parent = machine__findnew_thread(machine,
> >  							event->fork.ppid,
> >  							event->fork.ptid);
> > +	bool do_maps_clone = true;
> >  	int err = 0;
> >  
> >  	if (dump_trace)
> > @@ -1737,8 +1738,11 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event
> >  	thread = machine__findnew_thread(machine, event->fork.pid,
> >  					 event->fork.tid);
> >  
> > +	if (event->fork.header.misc & PERF_RECORD_MISC_FORK_EXEC)
> > +		do_maps_clone = false;
> 
> could you please put some comment in here shortly
> explaining the reason behind this flag

I'll get that comment from the commit log message
 
> > +
> >  	if (thread == NULL || parent == NULL ||
> > -	    thread__fork(thread, parent, sample->time) < 0) {
> > +	    thread__fork(thread, parent, sample->time, do_maps_clone) < 0) {
> >  		dump_printf("problem processing PERF_RECORD_FORK, skipping event.\n");
> >  		err = -1;
> >  	}
> > diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
> > index 2048d393ece6..54b2c9ceba9f 100644
> > --- a/tools/perf/util/thread.c
> > +++ b/tools/perf/util/thread.c
> > @@ -330,7 +330,8 @@ static int thread__prepare_access(struct thread *thread)
> >  }
> >  
> >  static int thread__clone_map_groups(struct thread *thread,
> > -				    struct thread *parent)
> > +				    struct thread *parent,
> > +				    bool do_maps_clone)
> >  {
> >  	/* This is new thread, we share map groups for process. */
> >  	if (thread->pid_ == parent->pid_)
> > @@ -341,15 +342,14 @@ static int thread__clone_map_groups(struct thread *thread,
> >  			 thread->pid_, thread->tid, parent->pid_, parent->tid);
> >  		return 0;
> >  	}
> > -
> >  	/* But this one is new process, copy maps. */
> > -	if (map_groups__clone(thread, parent->mg) < 0)
> > +	if (do_maps_clone &&
> > +	    map_groups__clone(thread, parent->mg) < 0)
> >  		return -ENOMEM;
> > -
> >  	return 0;
> 
> we could move all this into one line:
> 
> 	return do_maps_clone ? map_groups__clone(thread, parent->mg) : 0;

Yeah, I can do that as well, after looking at what map_groups__clone()
returns, which can go into the unwind backends.

- Arnaldo
 
> thanks,
> jirka
> 
> >  }
> >  
> > -int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp)
> > +int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp, bool do_maps_clone)
> >  {
> >  	if (parent->comm_set) {
> >  		const char *comm = thread__comm_str(parent);
> > @@ -362,7 +362,7 @@ int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp)
> >  	}
> >  
> >  	thread->ppid = parent->tid;
> > -	return thread__clone_map_groups(thread, parent);
> > +	return thread__clone_map_groups(thread, parent, do_maps_clone);
> >  }
> >  
> >  void thread__find_cpumode_addr_location(struct thread *thread, u64 addr,
> > diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
> > index 07606aa6998d..7e30fe99b74b 100644
> > --- a/tools/perf/util/thread.h
> > +++ b/tools/perf/util/thread.h
> > @@ -87,7 +87,7 @@ struct comm *thread__comm(const struct thread *thread);
> >  struct comm *thread__exec_comm(const struct thread *thread);
> >  const char *thread__comm_str(const struct thread *thread);
> >  int thread__insert_map(struct thread *thread, struct map *map);
> > -int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp);
> > +int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp, bool do_maps_clone);
> >  size_t thread__fprintf(struct thread *thread, FILE *fp);
> >  
> >  struct thread *thread__main_thread(struct machine *machine, struct thread *thread);

^ permalink raw reply	[flat|nested] 5+ messages in thread

* [tip:perf/urgent] perf tools: Don't clone maps from parent when synthesizing forks
  2018-10-31  5:24 [PATCH] perf: Don't clone maps from parent when synthesizing forks David Miller
  2018-10-31 13:00 ` Arnaldo Carvalho de Melo
  2018-10-31 13:01 ` Jiri Olsa
@ 2018-10-31 22:12 ` tip-bot for David Miller
  2 siblings, 0 replies; 5+ messages in thread
From: tip-bot for David Miller @ 2018-10-31 22:12 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: acme, dzickus, jolsa, davem, jmario, tglx, linux-kernel, mingo, hpa

Commit-ID:  4f8f382e635707ddaddf8269a116e4f8cc8835c0
Gitweb:     https://git.kernel.org/tip/4f8f382e635707ddaddf8269a116e4f8cc8835c0
Author:     David Miller <davem@davemloft.net>
AuthorDate: Tue, 30 Oct 2018 22:24:04 -0700
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Wed, 31 Oct 2018 10:18:01 -0300

perf tools: Don't clone maps from parent when synthesizing forks

When synthesizing FORK events, we are trying to create thread objects
for the already running tasks on the machine.

Normally, for a kernel FORK event, we want to clone the parent's maps
because that is what the kernel just did.

But when synthesizing, this should not be done.  If we do, we end up
with overlapping maps as we process the sythesized MMAP2 events that
get delivered shortly thereafter.

Use the FORK event misc flags in an internal way to signal this
situation, so we can elide the map clone when appropriate.

Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joe Mario <jmario@redhat.com>
Link: http://lkml.kernel.org/r/20181030.222404.2085088822877051075.davem@davemloft.net
[ Added comment about flag use in machine__process_fork_event(),
  use ternary op in thread__clone_map_groups() as suggested by Jiri ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 include/uapi/linux/perf_event.h       |  2 ++
 tools/include/uapi/linux/perf_event.h |  2 ++
 tools/perf/util/event.c               |  1 +
 tools/perf/util/machine.c             | 19 ++++++++++++++++++-
 tools/perf/util/thread.c              | 13 +++++--------
 tools/perf/util/thread.h              |  2 +-
 6 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index f35eb72739c0..9de8780ac8d9 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -646,10 +646,12 @@ struct perf_event_mmap_page {
  *
  *   PERF_RECORD_MISC_MMAP_DATA  - PERF_RECORD_MMAP* events
  *   PERF_RECORD_MISC_COMM_EXEC  - PERF_RECORD_COMM event
+ *   PERF_RECORD_MISC_FORK_EXEC  - PERF_RECORD_FORK event (perf internal)
  *   PERF_RECORD_MISC_SWITCH_OUT - PERF_RECORD_SWITCH* events
  */
 #define PERF_RECORD_MISC_MMAP_DATA		(1 << 13)
 #define PERF_RECORD_MISC_COMM_EXEC		(1 << 13)
+#define PERF_RECORD_MISC_FORK_EXEC		(1 << 13)
 #define PERF_RECORD_MISC_SWITCH_OUT		(1 << 13)
 /*
  * These PERF_RECORD_MISC_* flags below are safely reused
diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
index f35eb72739c0..9de8780ac8d9 100644
--- a/tools/include/uapi/linux/perf_event.h
+++ b/tools/include/uapi/linux/perf_event.h
@@ -646,10 +646,12 @@ struct perf_event_mmap_page {
  *
  *   PERF_RECORD_MISC_MMAP_DATA  - PERF_RECORD_MMAP* events
  *   PERF_RECORD_MISC_COMM_EXEC  - PERF_RECORD_COMM event
+ *   PERF_RECORD_MISC_FORK_EXEC  - PERF_RECORD_FORK event (perf internal)
  *   PERF_RECORD_MISC_SWITCH_OUT - PERF_RECORD_SWITCH* events
  */
 #define PERF_RECORD_MISC_MMAP_DATA		(1 << 13)
 #define PERF_RECORD_MISC_COMM_EXEC		(1 << 13)
+#define PERF_RECORD_MISC_FORK_EXEC		(1 << 13)
 #define PERF_RECORD_MISC_SWITCH_OUT		(1 << 13)
 /*
  * These PERF_RECORD_MISC_* flags below are safely reused
diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index bc646185f8d9..e9c108a6b1c3 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -308,6 +308,7 @@ static int perf_event__synthesize_fork(struct perf_tool *tool,
 	event->fork.pid  = tgid;
 	event->fork.tid  = pid;
 	event->fork.header.type = PERF_RECORD_FORK;
+	event->fork.header.misc = PERF_RECORD_MISC_FORK_EXEC;
 
 	event->fork.header.size = (sizeof(event->fork) + machine->id_hdr_size);
 
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 8ee8ab39d8ac..8f36ce813bc5 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1708,6 +1708,7 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event
 	struct thread *parent = machine__findnew_thread(machine,
 							event->fork.ppid,
 							event->fork.ptid);
+	bool do_maps_clone = true;
 	int err = 0;
 
 	if (dump_trace)
@@ -1736,9 +1737,25 @@ int machine__process_fork_event(struct machine *machine, union perf_event *event
 
 	thread = machine__findnew_thread(machine, event->fork.pid,
 					 event->fork.tid);
+	/*
+	 * When synthesizing FORK events, we are trying to create thread
+	 * objects for the already running tasks on the machine.
+	 *
+	 * Normally, for a kernel FORK event, we want to clone the parent's
+	 * maps because that is what the kernel just did.
+	 *
+	 * But when synthesizing, this should not be done.  If we do, we end up
+	 * with overlapping maps as we process the sythesized MMAP2 events that
+	 * get delivered shortly thereafter.
+	 *
+	 * Use the FORK event misc flags in an internal way to signal this
+	 * situation, so we can elide the map clone when appropriate.
+	 */
+	if (event->fork.header.misc & PERF_RECORD_MISC_FORK_EXEC)
+		do_maps_clone = false;
 
 	if (thread == NULL || parent == NULL ||
-	    thread__fork(thread, parent, sample->time) < 0) {
+	    thread__fork(thread, parent, sample->time, do_maps_clone) < 0) {
 		dump_printf("problem processing PERF_RECORD_FORK, skipping event.\n");
 		err = -1;
 	}
diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index 2048d393ece6..3d9ed7d0e281 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -330,7 +330,8 @@ static int thread__prepare_access(struct thread *thread)
 }
 
 static int thread__clone_map_groups(struct thread *thread,
-				    struct thread *parent)
+				    struct thread *parent,
+				    bool do_maps_clone)
 {
 	/* This is new thread, we share map groups for process. */
 	if (thread->pid_ == parent->pid_)
@@ -341,15 +342,11 @@ static int thread__clone_map_groups(struct thread *thread,
 			 thread->pid_, thread->tid, parent->pid_, parent->tid);
 		return 0;
 	}
-
 	/* But this one is new process, copy maps. */
-	if (map_groups__clone(thread, parent->mg) < 0)
-		return -ENOMEM;
-
-	return 0;
+	return do_maps_clone ? map_groups__clone(thread, parent->mg) : 0;
 }
 
-int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp)
+int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp, bool do_maps_clone)
 {
 	if (parent->comm_set) {
 		const char *comm = thread__comm_str(parent);
@@ -362,7 +359,7 @@ int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp)
 	}
 
 	thread->ppid = parent->tid;
-	return thread__clone_map_groups(thread, parent);
+	return thread__clone_map_groups(thread, parent, do_maps_clone);
 }
 
 void thread__find_cpumode_addr_location(struct thread *thread, u64 addr,
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index 36c09a9904e6..30e2b4c165fe 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -89,7 +89,7 @@ struct comm *thread__comm(const struct thread *thread);
 struct comm *thread__exec_comm(const struct thread *thread);
 const char *thread__comm_str(const struct thread *thread);
 int thread__insert_map(struct thread *thread, struct map *map);
-int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp);
+int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp, bool do_maps_clone);
 size_t thread__fprintf(struct thread *thread, FILE *fp);
 
 struct thread *thread__main_thread(struct machine *machine, struct thread *thread);

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2018-10-31 22:12 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-10-31  5:24 [PATCH] perf: Don't clone maps from parent when synthesizing forks David Miller
2018-10-31 13:00 ` Arnaldo Carvalho de Melo
2018-10-31 13:01 ` Jiri Olsa
2018-10-31 13:06   ` Arnaldo Carvalho de Melo
2018-10-31 22:12 ` [tip:perf/urgent] perf tools: " tip-bot for David Miller

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