>From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of >Hunkeler Peter (KIUK 3) Sent: Wednesday, March 11, 2009 8:39 AM To: [email protected] Subject: Re: How much does GTF trace impact system throughput?
>Bill, thanks for the insight. Much appreciated. >I only need two USR events (FD0 and FD4) that, as I understand it, PSF writes with the GTRACE macro. So GTF will then only need to listen for GTRACE events and that will reduce the overhead quite a bit, right? >I'll follow your advice to only start 1 GTF instance. >Peter Hunkeler CREDIT SUISSE I have no experience with tracing USR events, but USR events is also an "event class", so wherever the USR GTRACE macro has been imbedded in any IBM or other code that you are running there will be a program interrupt and entry into GTF's filtering logic. Your conclusion is correct, except that I think that DB2 also uses USR events a lot. If you are using DB2 heavily (and if DB2 does in fact use USR), then you may have lower overhead by tracing I/O interrupts. I don't know anything about how to filter USR events. Please let me know what happens. The only real way to quantify GTF overhead is to measure your system's CPU usage with GTF and without GTF, then compare the two numbers, and you might also need a CPU soaker to run at low priority to eat up all available CPU time that's left over when no other work is ready to run. Bill Fairchild Rocket Software ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
