Re: [dtrace-discuss] usdt probes vs pid$target
What about the expense of matching on the function name? You are saying that the kernel trap overwhelms that, right? On Sep 9, 2009, at 10:20 PM, Chad Mynhier wrote: No, it's not significantly more efficient. Both function entry/return probes and USDT probes involve replacing an instruction in the stream with a trap instruction. The expense of the trap into the kernel is going to overwhelm any subtleties in handling between the two different types of probes. --- fastest mac firefox! http://wagerlabs.com ___ dtrace-discuss mailing list dtrace-discuss@opensolaris.org
Re: [dtrace-discuss] usdt probes vs pid$target
To be more explicit, my concerns are about the effect of function name entry/return probes vs static probes on elapsed time, as measured by timestamp. I'm viewing all my timings as a percentage of total elapsed time and I'm wondering if there's less overhead in using static probes in this context. Thanks, Joel On Sep 9, 2009, at 10:20 PM, Chad Mynhier wrote: The expense of the trap into the kernel is going to overwhelm any subtleties in handling between the two different types of probes. --- fastest mac firefox! http://wagerlabs.com ___ dtrace-discuss mailing list dtrace-discuss@opensolaris.org
Re: [dtrace-discuss] usdt probes vs pid$target
On Sep 9, 2009, at 2:10 PM, Joel Reymont wrote: I'm wondering about my use, though. Is the following significantly more efficient than pid$target::FunName:entry and return? The cost of the actual probe firing is the same. The *eval-time* cost of finding out which probes exist and turning on the right ones is much faster in the USDT case. I heard somewhere that $target does not need to be used with static probes but the probes don't show up unless Firefox is running and then only as mozillaN, i.e. mozilla$target. Thanks, Joel You can wildcard the USDT probes: mozilla*:::process-xul-reflow-entry will match all existing processes with that probe, and any future ones that start up with that probe. James M ___ dtrace-discuss mailing list dtrace-discuss@opensolaris.org
