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SkyRiver-9129 avatar image
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SkyRiver-9129 asked ErlandSommarskog answered

SOS_SCHEDULER_YIELD is high during load testing

Run the wait stats SQL from https://www.sqlskills.com/blogs/paul/wait-statistics-or-please-tell-me-where-it-hurts/ got:

wait type: SOS_SCHEDULER_YIELD
Wait_S: 90611.23
Resource_S: 3.6
Signal_S: 90607.63
WaitCount: 4994846
Percentage: 90.33
AvgWait_S: 0.0181
AvgRes_S: 0.0000
AvgSig_S: 0.0181

Please advise if we do need more CPU or SQL tuning.

Thanks,
Sky

sql-server-general
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TomPhillips-1744 avatar image
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TomPhillips-1744 answered SkyRiver-9129 commented

The avg wait is 0.0181 seconds. That does not look like an issue to solve.

Are you having a problem of some kind?

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Thank you, I think it is not an issue, but Signal_S wait is high, 90607.63. Do you think we need do any tuning?

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ErlandSommarskog avatar image
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ErlandSommarskog answered

That's a question we cannot answer, because it all depends on the requirements. If there is a requirements that says that you must be able to process N operations (as defined by whatever your application is for) per minute, and in your test show that you are only able to process N/2, then you have something to work with. On the other hand, if you are able to process 2*N operations, just be happy and smile. Yes, it may still be that the system can be tuned, but do you think your boss/client will agree to spend money on that when the test passes with flying colours?

The wait stats is only of interest if you have determined that you need to do better.

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