cpu-speed | 易学教程

How to compute the theoretical peak performance of CPU

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问题 Here is my cat /proc/cpuinfo output: ... processor : 15 vendor_id : GenuineIntel cpu family : 6 model : 26 model name : Intel(R) Xeon(R) CPU E5520 @ 2.27GHz stepping : 5 cpu MHz : 1600.000 cache size : 8192 KB physical id : 1 siblings : 8 core id : 3 cpu cores : 4 apicid : 23 fpu : yes fpu_exception : yes cpuid level : 11 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic ... bogomips : 4533.56 clflush size : 64 cache_alignment : 64 address sizes : 40 bits physical, 48 bits virtual

Why is modulus operator slow?

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问题 Paraphrasing from in "Programming Pearls" book (about c language on older machines, since book is from the late 90's): Integer arithmetic operations ( + , - , * ) can take around 10 nano seconds whereas the % operator takes up to 100 nano seconds. Why there is that much difference? How does a modulus operator work internally? Is it same as division ( / ) in terms of time? 回答1: The modulus/modulo operation is usually understood as the integer equivalent of the remainder operation - a side

How to profile django application with respect to execution time?

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问题 My Django application is insanely slow, I want to figure out what is taking time : I tried Django-debug-toolbar but was unable to find a panel that can give me the break-up of the load time. My requirements: A stack-trace type output with time of execution for each module called to render the page. I want to realize what part of the whole page rendering process is taking the time ? Also, what part is consuming how much CPU [ MOST IMPORTANT ] ? Can django-debug-toolbar do that ? [ What panel ?

How can I programmatically find the CPU frequency with C

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I'm trying to find out if there is anyway to get an idea of the CPU frequency of the system my C code is running on. To clarify, I'm looking for an abstract solution, (one that will not be tied to a specific architecture or OS) which can give me an idea of the operating frequency of the computer that my code is executing on. I don't need to be exact, but I'd like to be in the ball park (ie. I have a 2.2GHz processor, I'd like to be able to tell in my program that I'm within a few hundred MHz of that) Does anyone have an idea use standard C code? Yunchi How you find the CPU frequency is both

How has CPU architecture evolution affected virtual function call performance?

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Years ago I was learning about x86 assembler, CPU pipelining, cache misses, branch prediction, and all that jazz. It was a tale of two halves. I read about all the wonderful advantages of the lengthy pipelines in the processor viz instruction reordering, cache preloading, dependency interleaving, etc. The downside was that any deviation for the norm was enormously costly. For example, IIRC a certain AMD processor in the early-gigahertz era had a 40 cycle penalty every time you called a function through a pointer (!) and this was apparently normal. This is not a negligible "don't worry about it

Does multi-threading improve performance? How?

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I hear everyone talking about how multi-threading can improve performance. I don't believe this, unless there is something I'm missing. If I have an array of 100 elements and traversing it takes 6 seconds. When I divide the work between two threads, the processor would have to go through the same amount of work and therefore time, except that they are working simultaneously but at half the speed. Shouldn't multi threading make it even slower? Since you need additional instructions for dividing the work? For a simple task of iterating 100 elements multi-threading the task will not provide a

I need to call accurate CPU usage of a single process

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问题 The Trick is I also need to be able to do it on multi core machines. My education in C# is a tad broken. I have managed the following code. Can anyone help me out? Iv tried using the "_Total" flag and I have tried modifying some other code snippets that looked like they tried to detect the amount of cores. I was told however they did not include HT and only supported physical not logical processors. I was trying to get it to do both. Apparently their is a way to manually do this using (

Finding out the CPU clock frequency (per core, per processor)

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Programs like CPUz are very good at giving in depth information about the system (bus speed, memory timings, etc.) However, is there a programmatic way of calculating the per core (and per processor, in multi processor systems with multiple cores per CPU) frequency without having to deal with CPU specific info. I am trying to develop a anti cheating tool (for use with clock limited benchmark competitions) which will be able to record the CPU clock during the benchmark run for all the active cores in the system (across all processors.) I'll expand on my comments here. This is too big and in

How has CPU architecture evolution affected virtual function call performance?

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问题 Years ago I was learning about x86 assembler, CPU pipelining, cache misses, branch prediction, and all that jazz. It was a tale of two halves. I read about all the wonderful advantages of the lengthy pipelines in the processor viz instruction reordering, cache preloading, dependency interleaving, etc. The downside was that any deviation for the norm was enormously costly. For example, IIRC a certain AMD processor in the early-gigahertz era had a 40 cycle penalty every time you called a

How to detect android cpu speed?

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问题 I would like to detect how fast is the device on which my Android application is running? Is there any API to do it on Android? Or do I have to benchmark it by myself? If the device has slow CPU I would like to turn off some time consuming operations like animations or limit maximum number of simultaneous HTTP request. 回答1: The best way to do it in my opinion is to monitor the time it takes to do these actions. If it is taking too much time, then the system is too slow and you can disable