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Re: dtrace, profile and ustack
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Re: dtrace, profile and ustack


  • Subject: Re: dtrace, profile and ustack
  • From: Eric Gouriou <email@hidden>
  • Date: Mon, 24 Aug 2009 17:51:55 -0700


On Aug 24, 2009, at 4:02 PM, Joel Reymont wrote:
I get a bunch of memory access errors when trying to run my script, e.g.

dtrace: script 'high.d' matched 2 probes
dtrace: allowing destructive actions
dtrace: error on enabled probe ID 1 (ID 36: profile:::profile-997): invalid address (0xbffff7c8) in action #2
dtrace: error on enabled probe ID 1 (ID 36: profile:::profile-997): invalid address (0xbfffca28) in action #2
dtrace: error on enabled probe ID 1 (ID 36: profile:::profile-997): invalid address (0xbfffcb58) in action #2


The script is trying to determine the hot paths through initialization of firefox (up to main), e.g.

profile-997
/pid == $target/
{
@[ustack()] = count()
}

/* stop tracing here */

pid$target:XUL:XRE_main:entry
{
exit(0);
}

END
{
trunc(@, 25)
}

Any suggestions on how to avoid the non-paged memory errors above?

I'd recommend using Instruments and/or Shark for such profiles. The DTrace profile
probe cannot give you this information at this time, as ustack() is not effective from
the environment where profile probes get triggered. If I remember correctly
that's due to not being able to take page faults in that environment.


Don't forget to file a bug report about this.

  Eric

PS: <email@hidden> might be a better place to hit
people more specialized towards performance work.


	Thanks, Joel

---
fastest mac firefox!
http://wagerlabs.com

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  • Follow-Ups:
    • Re: dtrace, profile and ustack
      • From: Wade Tregaskis <email@hidden>
References: 
 >dtrace, profile and ustack (From: Joel Reymont <email@hidden>)

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