Affinity
Anything related to processor affinity, also known as CPU pinning
Cpu
The central processing unit or "processor" inside a computer which executes the instructions in a computer program.
Performance vs changes
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"Also note - if rdtsc is used without an invariant time source on linux grep constant_tsc proc cpuinfo you may get unreliable values across frequency changes and if the task switches cpu time source;so in general yes setting the affinity does gives lower latency but this is not always true and there are very serious costs when you do this" from question Should I "bind" "spinning" thread to the certain core? |
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"But i found if i do not set their cpu affinity that is they run on same core 0 the time performance get better than setting cpu affinity 8.76s vs 14.66s" from question Why settting CPU affinity make threads run slower? "Cpu affinity it s better for the cpu to have a load average of 1.0 and processes to have affinity to a single core" from question Bad Django / uwsgi performance |
Others
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Cpu is multicore user-space app will have affinity to one core from question Kernel to user space communication with low latency |
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So you may be starving ssis of cpu not memory;you could try changing processors affinity to allow sql server to use only 16 cores and let the memory find it s own level from question SQL Server 2005 Instance memory allocation and SSIS DTSExec performance |
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Further more in deadline scheduling kernel rejects setting when cpu affinity mask is smaller than the entire root_domain in what case would cpu affinity mask become smaller than the root_domain span from question Difference between struct root_domain and struct sched_domain |
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The cpu affinity is more like a suggestion to the kernel regarding which cpu to use from question Wait for pid end signal |
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With a query that doesn t end up blocking on resources on a 4-core machine you theoretically get a 4-times speed up 4 hyper-threaded might give you more or even less but probably not 8-times since hyperthreading s doubling of some parts of the cpu doesn t give a clear two-times increase;with the same query on a single-core or with processors affinity meaning only one core is available a webserver in web-garden mode then there s no speed-up from question Difference linq and plinq |
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Use irq affinity to set other cpus to handle all interrupts so that your isolated cpu will not receive any interrupts;use cpu affinity to fix your specific task to the isolated cpu from question Whole one core dedicated to single process |