From: Dave J. <da...@su...> - 2001-10-13 23:52:02
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Hi guys, I've been reading about Intels vtune app. (Currently windows only, but according to http://www.linux-clusters-institute.org/program.html there may be a port at some point). From what I've been reading, it seems that it can profile an entire application in one go, and then show the values of all available counters. This got me thinking. What kind of overhead do we have for switching a counter from one event to another ? I'm wondering if they're not just somehow switching the event being monitored every so often. any further ideas ? regards, Dave. -- | Dave Jones. http://www.codemonkey.org.uk | SuSE Labs . |
From: Gareth H. <gar...@ac...> - 2001-10-13 23:59:25
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Dave Jones wrote: > Hi guys, > I've been reading about Intels vtune app. (Currently windows only, > but according to http://www.linux-clusters-institute.org/program.html > there may be a port at some point). > >>From what I've been reading, it seems that it can profile an > entire application in one go, and then show the values of all > available counters. This got me thinking. What kind of overhead > do we have for switching a counter from one event to another ? > I'm wondering if they're not just somehow switching the event > being monitored every so often. > > any further ideas ? I have used VTune 4.5 quite a bit, and in my experience when you select multiple counters it runs the app that many times with one counter enabled each time. This behaviour may have changed in v5.0. -- Gareth |
From: Dave J. <da...@su...> - 2001-10-14 00:04:33
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On Sat, 13 Oct 2001, Gareth Hughes wrote: > I have used VTune 4.5 quite a bit, and in my experience when you select > multiple counters it runs the app that many times with one counter > enabled each time. This behaviour may have changed in v5.0. Ah, thats cheating :-) Given the hardware limitation, unless they're doing something clever, its probably the same in the latest version. I'll try out the demo version when I find a windows box sometime. regards, Dave -- | Dave Jones. http://www.codemonkey.org.uk | SuSE Labs |
From: John L. <mo...@co...> - 2001-10-14 01:25:23
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On Sun, Oct 14, 2001 at 02:04:26AM +0200, Dave Jones wrote: > Given the hardware limitation, unless they're doing something clever, > its probably the same in the latest version. I'll try out the demo > version when I find a windows box sometime. The "Where have all the cycles gone ?" DEC paper from which the basic oprofile idea was borrowed does make reference to an event multiplexing facility in DCPI. I'm not familiar with the alpha counters, and the paper is sketchy on details. It might be worth checking out the DCPI documentation. I expect it works simply by changing event type each interrupt and adding an event tag to the profiling structures - at a sufficiently high rate I suppose this might come out with something useful over longer runs. regards john -- "Please crack down on the Chinaman's friends and Hitler's commander. Mother is the best bet and don't let Satan draw you too fast. A boy has never wept ... nor dashed a thousand kim. Did you hear me?" - Dutch Schultz |