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mfcking
Beginner
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Does each thread in Hyper-Threading have its own performance counters?

Hi,
VTune gives the clock ticks for each thread when hyper-threading is enabled. Does this mean each thread have its own performance counters? I thought only physical CPU has performance counters. Buthow can VTune tell how long each thread has run?
Another question is, unlike physical CPU, how to define a logical CPU is busy or not? The reason I ask this question is: we found although top command reported both logical CPU (thread) are 100% busy, actually one thread handled90% of workload and another threadtool care of the rest of 10% by checking the number of interrupts routed to each thread. This is understandable based on the concept of hyper-threading, i.e. another thread will get the chance to run only the current thread is stalled. Is vtune aware of the different between physical CPU and logical thread?
Thanks,
L.Y.

Message Edited by mfcking@yahoo.com on 12-14-2005 02:22 PM

Message Edited by mfcking@yahoo.com on 12-14-2005 02:35 PM

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2 Replies
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Quick aside here: if anybody who reads this is interested in thread performance in general, be sure to check out the Intel Threading Tools, here.

You can download evaluation versions of the Intel Thread Checker and Intel Thread Profiler and kick the tires on them. (The Checker looks for actual errors and reports them; the Profiler helps you find peformance issues regarding synchronization, thread imbalances, etc.)

These work with the VTune GUI. They're a must for anybody doing thread optimization work.

cheers

jdg

David_A_Intel1
Employee
73 Views

The short answer is, no.

Rather, each counter can be either thread-specific or thread-independent. See the online help for the processor your are using, and review the events. Some will with 'TI' after them, some 'TI-E',and some 'AT-E' (depending on your processor; use 'vtl query -c sampling' to dump the list of events supported by your processor).

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