dtrace discuss - Sep 2009 - Why is plockstat provider only present for 1 process

Hi,

I would like to know why dtrace -l |grep plockstat show plockstat28099
lines.
Process with pid 28099 is a java process.

Why can I not examine other processes with the plockstat provider?
Is it a java startup option?

Regards Hans
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Hi,

Can someone explain the difference between the lockstat and plockstat
provider?

Regards Hans
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Sloot, Hans-Peter wrote:
> Hi,
> 
> Can someone explain the difference between the lockstat and plockstat 
> provider?
lockstat is for the kernel.  plockstat is for user
''p''rocesses.

Hi Hans,
> I would like to know why dtrace -l |grep plockstat show plockstat28099 
> lines.
> Process with pid 28099 is a java process.
>
> Why can I not examine other processes with the plockstat provider?
> Is it a java startup option?
>
No. The probes that plockstat uses only become visible when you
actually run the plockstat(1M) command against a running process.
We create them in a lazy manner like this because the probes that
plockstat relies upon are in libc and we don''t want to create these
probes every time a process starts (and destroy them when it exits).

If you run plockstat against any other process then you''ll now
see the probess when you execute `dtrace -l -P plockstat*`.

Jon.

Ok thanks.

It works!

 

-----Original Message-----
From: Jonathan.Haslam at Sun.COM [mailto:Jonathan.Haslam at Sun.COM] 
Sent: Friday, September 18, 2009 11:30
To: Sloot, Hans-Peter
Cc: dtrace-discuss at opensolaris.org
Subject: Re: [dtrace-discuss] Why is plockstat provider only present for
1 process

Hi Hans,
> I would like to know why dtrace -l |grep plockstat show plockstat28099
> lines.
> Process with pid 28099 is a java process.
>
> Why can I not examine other processes with the plockstat provider?
> Is it a java startup option?
>
No. The probes that plockstat uses only become visible when you actually
run the plockstat(1M) command against a running process.
We create them in a lazy manner like this because the probes that
plockstat relies upon are in libc and we don''t want to create these
probes every time a process starts (and destroy them when it exits).

If you run plockstat against any other process then you''ll now see the
probess when you execute `dtrace -l -P plockstat*`.

Jon.

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Hi Jon,

Does the same apply for the pid provider?

I have seen pid<processid> providers with dtrace -l.
At the moment the command does not list any pid providers.

Regards Hans 

-----Original Message-----
From: Jonathan.Haslam at Sun.COM [mailto:Jonathan.Haslam at Sun.COM] 
Sent: Friday, September 18, 2009 11:30
To: Sloot, Hans-Peter
Cc: dtrace-discuss at opensolaris.org
Subject: Re: [dtrace-discuss] Why is plockstat provider only present for
1 process

Hi Hans,
> I would like to know why dtrace -l |grep plockstat show plockstat28099
> lines.
> Process with pid 28099 is a java process.
>
> Why can I not examine other processes with the plockstat provider?
> Is it a java startup option?
>
No. The probes that plockstat uses only become visible when you actually
run the plockstat(1M) command against a running process.
We create them in a lazy manner like this because the probes that
plockstat relies upon are in libc and we don''t want to create these
probes every time a process starts (and destroy them when it exits).

If you run plockstat against any other process then you''ll now see the
probess when you execute `dtrace -l -P plockstat*`.

Jon.

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> Does the same apply for the pid provider?
>
> I have seen pid<processid> providers with dtrace -l.
> At the moment the command does not list any pid providers.
Yes, pid provider probes won''t appear in the ouput of `dtrace -l`
until they have been explicitly created (by enabling them):

# dtrace -l -P pid*
   ID   PROVIDER            MODULE                          FUNCTION NAME
dtrace: failed to match pid*:::: No probe matches description
# pgrep -fl nscd
  845 /usr/sbin/nscd
# dtrace -n ''pid$1:libc:printf:entry'' `pgrep nscd`
dtrace: description ''pid$1:libc:printf:entry'' matched 1 probe
^C
# dtrace -l -P pid*
   ID   PROVIDER            MODULE                          FUNCTION NAME
59613     pid845         libc.so.1                            printf entry

This probe will hang around until the process in question exits.

Jon.
> Regards Hans 
>
> -----Original Message-----
> From: Jonathan.Haslam at Sun.COM [mailto:Jonathan.Haslam at Sun.COM] 
> Sent: Friday, September 18, 2009 11:30
> To: Sloot, Hans-Peter
> Cc: dtrace-discuss at opensolaris.org
> Subject: Re: [dtrace-discuss] Why is plockstat provider only present for
> 1 process
>
> Hi Hans,
>
>   
>> I would like to know why dtrace -l |grep plockstat show plockstat28099
>>     
>
>   
>> lines.
>> Process with pid 28099 is a java process.
>>
>> Why can I not examine other processes with the plockstat provider?
>> Is it a java startup option?
>>
>>     
>
> No. The probes that plockstat uses only become visible when you actually
> run the plockstat(1M) command against a running process.
> We create them in a lazy manner like this because the probes that
> plockstat relies upon are in libc and we don''t want to create
these
> probes every time a process starts (and destroy them when it exits).
>
> If you run plockstat against any other process then you''ll now see
the
> probess when you execute `dtrace -l -P plockstat*`.
>
> Jon.
>
>

Thanks a lot!
Another mistery solved.
 

-----Original Message-----
From: Jonathan.Haslam at Sun.COM [mailto:Jonathan.Haslam at Sun.COM] 
Sent: Friday, September 18, 2009 12:21
To: Sloot, Hans-Peter
Cc: dtrace-discuss at opensolaris.org
Subject: Re: [dtrace-discuss] Why is plockstat provider only present for
1 process

> Does the same apply for the pid provider?
>
> I have seen pid<processid> providers with dtrace -l.
> At the moment the command does not list any pid providers.
Yes, pid provider probes won''t appear in the ouput of `dtrace -l` until
they have been explicitly created (by enabling them):

# dtrace -l -P pid*
   ID   PROVIDER            MODULE                          FUNCTION
NAME
dtrace: failed to match pid*:::: No probe matches description # pgrep
-fl nscd
  845 /usr/sbin/nscd
# dtrace -n ''pid$1:libc:printf:entry'' `pgrep nscd`
dtrace: description ''pid$1:libc:printf:entry'' matched 1 probe
^C #
dtrace -l -P pid*
   ID   PROVIDER            MODULE                          FUNCTION
NAME
59613     pid845         libc.so.1                            printf
entry

This probe will hang around until the process in question exits.

Jon.
> Regards Hans
>
> -----Original Message-----
> From: Jonathan.Haslam at Sun.COM [mailto:Jonathan.Haslam at Sun.COM]
> Sent: Friday, September 18, 2009 11:30
> To: Sloot, Hans-Peter
> Cc: dtrace-discuss at opensolaris.org
> Subject: Re: [dtrace-discuss] Why is plockstat provider only present 
> for
> 1 process
>
> Hi Hans,
>
>   
>> I would like to know why dtrace -l |grep plockstat show 
>> plockstat28099
>>     
>
>   
>> lines.
>> Process with pid 28099 is a java process.
>>
>> Why can I not examine other processes with the plockstat provider?
>> Is it a java startup option?
>>
>>     
>
> No. The probes that plockstat uses only become visible when you 
> actually run the plockstat(1M) command against a running process.
> We create them in a lazy manner like this because the probes that 
> plockstat relies upon are in libc and we don''t want to create
these
> probes every time a process starts (and destroy them when it exits).
>
> If you run plockstat against any other process then you''ll now see
the
> probess when you execute `dtrace -l -P plockstat*`.
>
> Jon.
>
>   

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