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剖析程序的内存布局 - C/C++ - 清泛网 - 专注C/C++及内核技术
...位模式下它总是一个4GB的内存地址块。这些虚拟地址通过页表（page table）映射到物理内存，页表由操作系统维护并被处理器引用。每一个进程拥有一套属于它自己的页表，但是还有一个隐情。只要虚拟地址被使能，那么它就会...
内存优化总结:ptmalloc、tcmalloc和jemalloc - 操作系统(内核) - 清泛网 - ...
... 总共32个vcpu。 16个table，每个5M row。
OLTP_RO测试包含5个select查询：select_ranges, select_order_ranges, select_distinct_ranges, select_sum_ranges,
可以看到在多核心或者多线程的场景下， jemalloc和tcmalloc带来的tps增加非常明显。
参考资料
glibc...
Python argparse: Make at least one argument required
...tiple aspects of command line based program:
good design of command line
selecting/using proper parser
argparse offers a lot, but restricts possible scenarios and can become very complex.
With docopt things go much shorter while preserving readability and offering high degree of flexibility. If...
Background color of text in SVG
...or to SVG elements. You can do it programmatically with d3.
var text = d3.select("text");
var bbox = text.node().getBBox();
var padding = 2;
var rect = self.svg.insert("rect", "text")
.attr("x", bbox.x - padding)
.attr("y", bbox.y - padding)
.attr("width", bbox.width + (padding*2))
...
Creating a “logical exclusive or” operator in Java
...
Java does have a logical XOR operator, it is ^ (as in a ^ b).
Apart from that, you can't define new operators in Java.
Edit: Here's an example:
public static void main(String[] args) {
boolean[] all = { false, true };
for (boolean a : all...
Remove duplicates in the list using linq
...
var distinctItems = items.GroupBy(x => x.Id).Select(y => y.First());
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近期 Chrome 下 Discuz 兼容问题修复记录：AJAX 提交失效与移动链接误跳转 ...
...还伴随扩展注入报错，但关闭扩展后问题依旧存在
3. 页面没有明确报错，但提交后没有结果
原因：
Discuz 旧版很多“ajaxpost”实际上是通过隐藏 iframe 提交表单，再从 iframe 返回文档中读取结果。
这套老机制在新版 Chro...
What are bitwise operators?
...ns
00000001
which is not 0, so the flag does specify READ.
You can use XOR to toggle various bits. I've used this when using a flag to specify directional inputs (Up, Down, Left, Right). For example, if a sprite is moving horizontally, and I want it to turn around:
Up: 00000001
Down: ...
How to toggle a value in Python
...5
>>> x = total - x # toggle
>>> x
3
Solution using XOR
If the value toggles between 0 and 1, you can use a bitwise exclusive-or:
>>> x = 1
>>> x ^= 1
>>> x
0
>>> x ^= 1
>>> x
1
The technique generalizes to any pair of integers....
PHP中9大缓存技术总结 - 更多技术 - 清泛网 - 专注C/C++及内核技术
PHP中9大缓存技术总结1、全页面静态化缓存也就是将页面全部生成html静态页面，用户访问时直接访问的静态页面，而不会去走php服务器解析的流程。此种方式，在CMS...1、全页面静态化缓存
也就是将页面全部生成html静态页面，...