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how to listen to N channels? (dynamic select statement)
.... While waiting for an input channel to have a value this consumes all the CPU available. The whole point of select on multiple channels (without a default clause) is that it efficiently waits until at least one is ready without spinning.
– Dave C
Jun 29 '18 at...
What does the git index contain EXACTLY?
...ex Entry Offset Table (IEOT) extension
This patch enables addressing the CPU cost of loading the index by adding
additional data to the index that will allow us to efficiently multi-
thread the loading and conversion of cache entries.
It accomplishes this by adding an (optional) index extension th...
What are the main performance differences between varchar and nvarchar SQL Server data types?
... highlighting how bad nvarchar performance can be...
SQL Server uses high CPU when searching inside nvarchar strings
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Caveats of select/poll vs. epoll reactors in Twisted
...are active at any given time.
All this means that epoll will lead to less CPU usage for most workloads. As far as memory usage goes, it's a bit of a toss up. select does manage to represent all the necessary information in a highly compact way (one bit per file descriptor). And the FD_SETSIZE (t...
What's the difference between the atomic and nonatomic attributes?
...s the default behavior
will ensure the present process is completed by the CPU, before another process accesses the variable
is not fast, as it ensures the process is completed entirely
Non-Atomic
is NOT the default behavior
faster (for synthesized code, that is, for variables created using @prope...
deciding among subprocess, multiprocessing, and thread in Python?
...o threading while allowing CPython to scale your processing among multiple CPUs/cores despite the GIL (Global Interpreter Lock). It leverages all the fine-grained SMP locking and coherency effort that was done by developers of your OS kernel.
The threading option:
threading is for a fairly narrow r...
What is the performance of Objects/Arrays in JavaScript? (specifically for Google V8)
...
While running under node.js 0.10 (built on v8) I was seeing CPU usage that seemed excessive for the workload. I traced one performance problem to a function that was checking for the existence of a string in an array. So I ran some tests.
loaded 90,822 hosts
loading config took 0.08...
Best practices for circular shift (rotate) operations in C++
...shld edi,edi,7 which is slower and takes more bytes than rol edi,7 on some CPUs (especially AMD, but also some Intel), when BMI2 isn't available for rorx eax,edi,25 to save a MOV.
MSVC: x86-64 CL19: Only recognized for constant-count rotates. (The wikipedia idiom is recognized, but the branch and A...
现实版《道士下山》：道长老梁的四面人生 - 轻松一刻 - 清泛网 - 专注C/C++...
...前已经4皇冠；在“知乎”上，他解答了120个道教的相关问题，获得了7000个赞同；他还是道教题材的玄幻小说《返真》的作者，起点中文网A级签约作家……
在现实生活中，在金仙观里，却丝毫看不出他的“另类”，只是普通的...
Quickly find whether a value is present in a C array?
... this doesn't take into account memory delays.
Theory of operation: ARM's CPU design executes most instructions in one clock cycle, but the instructions are executed in a pipeline. C compilers will try to eliminate the pipeline delays by interleaving other instructions in between. When presented wi...