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SQL Server 2012’s Information on Parallel Thread Usage


SQL Server 2012’s Information on Parallel Thread Usage

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Joe Sack SQLskills
Joe Sack SQLskills
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Comments posted to this topic are about the item SQL Server 2012’s Information on Parallel Thread Usage
Rajib Bahar
Rajib Bahar
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I usually struggle w/ improving queries involving parallelism. Some dbas I've worked with recommended MAXDOP hint.

Even with those recommendations, I notice my queries some time don't use all available CPUs. I'd see it did the work with 8 CPU out of 24+ available to it. Is that necessarily a good thing? Sorry I hope I haven't deviated too much from your topic.

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joe.sack
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Hi Rajib,


In my example - I had 8 schedulers available but the 24 represents the threads reserved for the execution of the query (lifetime of the query).

Regarding queries sometimes not using all available CPUs, there are a few different areas to examine or consider.

The costing uses half of the available schedulers as an assumption. For example, in my article the costing was based on 4 but executed with 8. Feel free to share your specifics here and we can discuss further.



Cheers,

Joe
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