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Is thread_concurrency variable effective?
| Posted by mtrc, 12-18-2008, 05:02 PM |
| Is thread_concurrency variable effective?
It's recommended to make thread_concurrency = Number of CPU's x 2. But this is really effective with latest mysql5 versions?http://mysql.biz.net.id/doc/refman/5...ad_concurrency
Default 10
Range 1-512
Why to set it to 8 (4 cpus), for example, if recommended default value is 10? And why to set such a low value if range is till 512?
Anyone, any idea?
Also, how to check assigned value as "show variables;" command omit this value.
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| Posted by vapetrov, 12-19-2008, 01:04 AM |
| thread_concurrency - the number of processes which will run AT SAME TIME.
In all modern OSs possible to run a lot of tasks simultaneously. But in real one processor will perform ONE task at once but very frequently switch between tasks.
If you have few CPUs it possible to run few tasks really simultaneously.
Recomended value "Number of CPU's x 2" is for dedicated mysql servers only.
If you run a lot of other daemons (like apache, mail servers, etc.) it may be useful to set thread_concurrency to value equal to "Number of CPU" or even lower.
It may depends on type of you SQL queries and system configuration.
Best way - behchmark your system with different parameters.
But not expect too match from this parameter - probably you'll get only few (tens) percents of performance by tuning this parameter.
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| Posted by cywkevin, 12-19-2008, 03:32 AM |
| The last time I checked it only had an impact on Solaris systems. If in doubt benchmark it and test it but it probably still doesn't do anything. Keep in mind that 5.1 does have some configuration parameters that will allow you to tune threads specifically the thread_handling and thread_stack variables and do have an impact. Check the reference documentation accordingly.
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| Posted by mtrc, 12-19-2008, 05:02 AM |
| Any idea how to show assigned variable for thread_concurrency? As it is not included with 'show variables;'. I haven't see real improvement and I'm in doubt if it's active or not on mysql 5.0.45.-.51
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