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#1 21-08-2017 13:52:34

donnieclark
Membre
Date d'inscription: 12-05-2017
Messages: 363

Calculating Maximum Consumption Rate (MCR)

1) Why MAXDOP=4 is specified while MCR tends to calculate consumption rate for 1 core?

Since the calculations is      ( [Logical reads] / [CPU time in seconds] ) * 8KB / 1024

and there is 1 second of [CPU time in seconds]  per second for each core, the result is in MB/Core/sec in any case.  But if you evaluated with a single-threaded query you might overestimate the MCR as the limiting factor in a multi-threaded query might be memory transfer bandwidth.  As Thomas said, this is somewhat arbitrary, and they could have picked 2 or 6 or 8.

>What if my processor uses 25% of its maximum power when running the test query?

Since MAXDOP is limited in calculating MCR it's not expected to use 100% of your available CPU resources.  And the query used to measure MCR is simple: in a real world workload queries may require significantly more CPU/MB than the benchmark query.  So if you have free CPU resources while performing simple scan-oriented queries, then you will have resources available to perform additional query processing while scanning at your maximum rate.



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