Re: [PATCH 29/48] perf callchain: Maintain libunwind's address space in map_groups

From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Jiri Olsa <jolsa@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>,
	lkml <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Andi Kleen <andi@firstfloor.org>,
	Alexey Budankov <alexey.budankov@linux.intel.com>
Subject: Re: [PATCH 29/48] perf callchain: Maintain libunwind's address space in map_groups
Date: Fri, 14 Sep 2018 15:15:47 -0300	[thread overview]
Message-ID: <20180914181547.GB25154@kernel.org> (raw)
In-Reply-To: <20180913125450.21342-30-jolsa@kernel.org>

Em Thu, Sep 13, 2018 at 02:54:31PM +0200, Jiri Olsa escreveu:
> Currently the address_space was kept in thread struct but it's more
> appropriate to keep it in map_groups as it's maintained throughout
> exec's with timestamps.  Also we should not flush the address space
> after exec since it still can be accessed when used with an indexed
> data file.
> 
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Link: http://lkml.kernel.org/n/tip-hjryh6x2yfnrz8g0djhez24z@git.kernel.org
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>  tools/perf/util/map.h                    |  5 ++++-
>  tools/perf/util/thread.h                 |  1 -
>  tools/perf/util/unwind-libunwind-local.c | 28 ++++++++++++++----------
>  tools/perf/util/unwind-libunwind.c       |  9 ++++----
>  tools/perf/util/unwind.h                 |  7 +++---
>  5 files changed, 29 insertions(+), 21 deletions(-)
> 
> diff --git a/tools/perf/util/map.h b/tools/perf/util/map.h
> index 02c6f6962eb1..b1efe57b8563 100644
> --- a/tools/perf/util/map.h
> +++ b/tools/perf/util/map.h
> @@ -65,10 +65,13 @@ struct maps {
>  
>  struct map_groups {
>  	struct maps	 maps;
> -	struct machine	 *machine;
> +	struct machine	*machine;
>  	refcount_t	 refcnt;
>  	u64		 timestamp;
>  	struct list_head list;

Hey, avoid these distractions, this doesn't change anything and besides
having the * aligned with the names of non-pointers is what is common
practice, see for instance 'struct task_struct', 'struct inode', to name
just two widely used structs in the kernel source :-)

I'll get these two fixed up, i.e. remove the above hunk, align the one
below :-)

- Arnaldo

> +#ifdef HAVE_LIBUNWIND_SUPPORT
> +	void		*addr_space;
> +#endif
>  };
>  
>  struct map_groups *map_groups__new(struct machine *machine);
> diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
> index 86186a0773a0..637775f622b3 100644
> --- a/tools/perf/util/thread.h
> +++ b/tools/perf/util/thread.h
> @@ -40,7 +40,6 @@ struct thread {
>  	struct thread_stack	*ts;
>  	struct nsinfo		*nsinfo;
>  #ifdef HAVE_LIBUNWIND_SUPPORT
> -	void				*addr_space;
>  	struct unwind_libunwind_ops	*unwind_libunwind_ops;
>  #endif
>  };
> diff --git a/tools/perf/util/unwind-libunwind-local.c b/tools/perf/util/unwind-libunwind-local.c
> index da6f39315b47..f7c921f87bcf 100644
> --- a/tools/perf/util/unwind-libunwind-local.c
> +++ b/tools/perf/util/unwind-libunwind-local.c
> @@ -617,32 +617,35 @@ static unw_accessors_t accessors = {
>  	.get_proc_name		= get_proc_name,
>  };
>  
> -static int _unwind__prepare_access(struct thread *thread)
> +static int _unwind__prepare_access(struct map_groups *mg)
>  {
>  	if (!dwarf_callchain_users)
>  		return 0;
> -	thread->addr_space = unw_create_addr_space(&accessors, 0);
> -	if (!thread->addr_space) {
> +
> +	mg->addr_space = unw_create_addr_space(&accessors, 0);
> +	if (!mg->addr_space) {
>  		pr_err("unwind: Can't create unwind address space.\n");
>  		return -ENOMEM;
>  	}
>  
> -	unw_set_caching_policy(thread->addr_space, UNW_CACHE_GLOBAL);
> +	unw_set_caching_policy(mg->addr_space, UNW_CACHE_GLOBAL);
>  	return 0;
>  }
>  
> -static void _unwind__flush_access(struct thread *thread)
> +static void _unwind__flush_access(struct map_groups *mg)
>  {
>  	if (!dwarf_callchain_users)
>  		return;
> -	unw_flush_cache(thread->addr_space, 0, 0);
> +
> +	unw_flush_cache(mg->addr_space, 0, 0);
>  }
>  
> -static void _unwind__finish_access(struct thread *thread)
> +static void _unwind__finish_access(struct map_groups *mg)
>  {
>  	if (!dwarf_callchain_users)
>  		return;
> -	unw_destroy_addr_space(thread->addr_space);
> +
> +	unw_destroy_addr_space(mg->addr_space);
>  }
>  
>  static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
> @@ -650,7 +653,6 @@ static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
>  {
>  	u64 val;
>  	unw_word_t ips[max_stack];
> -	unw_addr_space_t addr_space;
>  	unw_cursor_t c;
>  	int ret, i = 0;
>  
> @@ -666,13 +668,15 @@ static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
>  	 * unwind itself.
>  	 */
>  	if (max_stack - 1 > 0) {
> +		struct map_groups *mg;
> +
>  		WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL");
> -		addr_space = ui->thread->addr_space;
>  
> -		if (addr_space == NULL)
> +		mg = thread__get_map_groups(ui->thread, ui->sample->time);
> +		if (mg == NULL || mg->addr_space == NULL)
>  			return -1;
>  
> -		ret = unw_init_remote(&c, addr_space, ui);
> +		ret = unw_init_remote(&c, mg->addr_space, ui);
>  		if (ret)
>  			display_error(ret);
>  
> diff --git a/tools/perf/util/unwind-libunwind.c b/tools/perf/util/unwind-libunwind.c
> index b029a5e9ae49..ce8408e460f2 100644
> --- a/tools/perf/util/unwind-libunwind.c
> +++ b/tools/perf/util/unwind-libunwind.c
> @@ -18,12 +18,13 @@ static void unwind__register_ops(struct thread *thread,
>  int unwind__prepare_access(struct thread *thread, struct map *map,
>  			   bool *initialized)
>  {
> +	struct map_groups *mg = thread->mg;
>  	const char *arch;
>  	enum dso_type dso_type;
>  	struct unwind_libunwind_ops *ops = local_unwind_libunwind_ops;
>  	int err;
>  
> -	if (thread->addr_space) {
> +	if (mg->addr_space) {
>  		pr_debug("unwind: thread map already set, dso=%s\n",
>  			 map->dso->name);
>  		if (initialized)
> @@ -56,7 +57,7 @@ int unwind__prepare_access(struct thread *thread, struct map *map,
>  out_register:
>  	unwind__register_ops(thread, ops);
>  
> -	err = thread->unwind_libunwind_ops->prepare_access(thread);
> +	err = thread->unwind_libunwind_ops->prepare_access(thread->mg);
>  	if (initialized)
>  		*initialized = err ? false : true;
>  	return err;
> @@ -65,13 +66,13 @@ int unwind__prepare_access(struct thread *thread, struct map *map,
>  void unwind__flush_access(struct thread *thread)
>  {
>  	if (thread->unwind_libunwind_ops)
> -		thread->unwind_libunwind_ops->flush_access(thread);
> +		thread->unwind_libunwind_ops->flush_access(thread->mg);
>  }
>  
>  void unwind__finish_access(struct thread *thread)
>  {
>  	if (thread->unwind_libunwind_ops)
> -		thread->unwind_libunwind_ops->finish_access(thread);
> +		thread->unwind_libunwind_ops->finish_access(thread->mg);
>  }
>  
>  int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
> diff --git a/tools/perf/util/unwind.h b/tools/perf/util/unwind.h
> index 8a44a1569a21..0f18a0858904 100644
> --- a/tools/perf/util/unwind.h
> +++ b/tools/perf/util/unwind.h
> @@ -9,6 +9,7 @@ struct map;
>  struct perf_sample;
>  struct symbol;
>  struct thread;
> +struct map_groups;
>  
>  struct unwind_entry {
>  	struct map	*map;
> @@ -19,9 +20,9 @@ struct unwind_entry {
>  typedef int (*unwind_entry_cb_t)(struct unwind_entry *entry, void *arg);
>  
>  struct unwind_libunwind_ops {
> -	int (*prepare_access)(struct thread *thread);
> -	void (*flush_access)(struct thread *thread);
> -	void (*finish_access)(struct thread *thread);
> +	int (*prepare_access)(struct map_groups *mg);
> +	void (*flush_access)(struct map_groups *mg);
> +	void (*finish_access)(struct map_groups *mg);
>  	int (*get_entries)(unwind_entry_cb_t cb, void *arg,
>  			   struct thread *thread,
>  			   struct perf_sample *data, int max_stack);
> -- 
> 2.17.1