Re: [PATCH] perf util: optimize util/machine.c:machines__find().

Re: [PATCH] perf util: optimize util/machine.c:machines__find().

[David Ahern]

On 11/21/13, 2:31 PM, Dongsheng Yang wrote:
> * Remove an unnecessary variable default_machine.
> * Return earlier to avoid unnecessary searching in children.
>
> Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
> ---
>   tools/perf/util/machine.c | 11 +++++------
>   1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 84cdb07..f0dd5f6 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -175,8 +175,7 @@ struct machine *machines__find(struct machines *machines, pid_t pid)
>   {
>   	struct rb_node **p = &machines->guests.rb_node;
>   	struct rb_node *parent = NULL;
> -	struct machine *machine;
> -	struct machine *default_machine = NULL;
> +	struct machine *machine = NULL;
>
>   	if (pid == HOST_KERNEL_ID)
>   		return &machines->host;
> @@ -184,17 +183,17 @@ struct machine *machines__find(struct machines *machines, pid_t pid)
>   	while (*p != NULL) {
>   		parent = *p;
>   		machine = rb_entry(parent, struct machine, rb_node);
> +		if (!machine->pid)
> +			break;
>   		if (pid < machine->pid)
>   			p = &(*p)->rb_left;
>   		else if (pid > machine->pid)
>   			p = &(*p)->rb_right;
>   		else
> -			return machine;
> -		if (!machine->pid)
> -			default_machine = machine;
> +			break;
>   	}
>
> -	return default_machine;
> +	return machine;
>   }

This changes machines__find to always return the machine for the host 
(pid == 0). This function is also used for VM lookups.

David

[PATCH] perf util: optimize util/machine.c:machines__find().

[Dongsheng Yang]

* Remove an unnecessary variable default_machine.
* Return earlier to avoid unnecessary searching in children.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
---
 tools/perf/util/machine.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 84cdb07..f0dd5f6 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -175,8 +175,7 @@ struct machine *machines__find(struct machines *machines, pid_t pid)
 {
 	struct rb_node **p = &machines->guests.rb_node;
 	struct rb_node *parent = NULL;
-	struct machine *machine;
-	struct machine *default_machine = NULL;
+	struct machine *machine = NULL;
 
 	if (pid == HOST_KERNEL_ID)
 		return &machines->host;
@@ -184,17 +183,17 @@ struct machine *machines__find(struct machines *machines, pid_t pid)
 	while (*p != NULL) {
 		parent = *p;
 		machine = rb_entry(parent, struct machine, rb_node);
+		if (!machine->pid)
+			break;
 		if (pid < machine->pid)
 			p = &(*p)->rb_left;
 		else if (pid > machine->pid)
 			p = &(*p)->rb_right;
 		else
-			return machine;
-		if (!machine->pid)
-			default_machine = machine;
+			break;
 	}
 
-	return default_machine;
+	return machine;
 }
 
 struct machine *machines__findnew(struct machines *machines, pid_t pid)
-- 
1.8.2.1

Re: [PATCH] perf util: optimize util/machine.c:machines__find().

[Arnaldo Carvalho de Melo]

Em Thu, Nov 21, 2013 at 02:16:26PM -0700, David Ahern escreveu:
> On 11/21/13, 2:31 PM, Dongsheng Yang wrote:
> >* Remove an unnecessary variable default_machine.
> >* Return earlier to avoid unnecessary searching in children.

> >Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>

> >+++ b/tools/perf/util/machine.c
> >@@ -175,8 +175,7 @@ struct machine *machines__find(struct machines *machines, pid_t pid)
> >  {
> >  	struct rb_node **p = &machines->guests.rb_node;
> >  	struct rb_node *parent = NULL;
> >-	struct machine *machine;
> >-	struct machine *default_machine = NULL;
> >+	struct machine *machine = NULL;
> >
> >  	if (pid == HOST_KERNEL_ID)
> >  		return &machines->host;
> >@@ -184,17 +183,17 @@ struct machine *machines__find(struct machines *machines, pid_t pid)
> >  	while (*p != NULL) {
> >  		parent = *p;
> >  		machine = rb_entry(parent, struct machine, rb_node);
> >+		if (!machine->pid)
> >+			break;
> >  		if (pid < machine->pid)
> >  			p = &(*p)->rb_left;
> >  		else if (pid > machine->pid)
> >  			p = &(*p)->rb_right;
> >  		else
> >-			return machine;
> >-		if (!machine->pid)
> >-			default_machine = machine;
> >+			break;
> >  	}
> >
> >-	return default_machine;
> >+	return machine;
> >  }
 
> This changes machines__find to always return the machine for the
> host (pid == 0). This function is also used for VM lookups.

Nope:

/* Native host kernel uses -1 as pid index in machine */
#define HOST_KERNEL_ID                  (-1)
#define DEFAULT_GUEST_KERNEL_ID         (0)

But I fail to see the point of the "optimization", we're looking for a
pid, not always for '0'.

And the changelog is horrible, why is it "unnecessary"? Please don't be
so terse :-)

- Arnaldo

Re: [PATCH] perf util: optimize util/machine.c:machines__find().

[Dongsheng Yang]

On 11/21/2013 07:06 PM, Arnaldo Carvalho de Melo wrote:
>
>> This changes machines__find to always return the machine for the
>> host (pid == 0). This function is also used for VM lookups.
> Nope:
>
> /* Native host kernel uses -1 as pid index in machine */
> #define HOST_KERNEL_ID                  (-1)
> #define DEFAULT_GUEST_KERNEL_ID         (0)
>
> But I fail to see the point of the "optimization", we're looking for a
> pid, not always for '0'.
>
> And the changelog is horrible, why is it "unnecessary"? Please don't be
> so terse :-)
>
> - Arnaldo
>

Hi David and Arnaldo,

     It is my mistake about it!! The original code does the right thing.
     Sorry to bother you, I am a newbie for perf.
     I will send a patch after second and third thought next time.

Thanx for your reply.

- Yang