cpu

Why do Compilers put data inside .text(code) section of the PE and ELF files and how does the CPU distinguish between data and code?

由 梦想与她 提交于 2020-01-11 03:02:08
问题 So i am referencing this paper : Binary Stirring: Self-randomizing Instruction Addresses of Legacy x86 Binary Code https://www.utdallas.edu/~hamlen/wartell12ccs.pdf Code interleaved with data: Modern compilers aggressively interleave static data within code sections in both PE and ELF binaries for performance reasons. In the compiled binaries there is generally no means of distinguishing the data bytes from the code. Inadvertently randomizing the data along with the code breaks the binary,

Retrieve system information on MacOS X? [closed]

由 ↘锁芯ラ 提交于 2020-01-10 03:17:09
问题 As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 8 years ago . Using C++ is there anyway I could get basic information about the computer? For example is there a way I could check how much memory

read CPU cache contents

由 夙愿已清 提交于 2020-01-09 19:07:21
问题 Is there any way to read the CPU cache contents? Architecture is for ARM. I m invalidating a range of addresses and then want to make sure whether it is invalidated or not. Although I can do read and write of the range of addresses with and without invalidating and checking the invalidation, I want to know whether it is possible to read the cache contents Thanks!! 回答1: ARM9 provides cache manipulation and test registers that allow you to examine the state of the cache. Here's a reasonable

Alignment along 4-byte boundaries

由 依然范特西╮ 提交于 2020-01-09 09:08:51
问题 I recently got thinking about alignment... It's something that we don't ordinarily have to consider, but I've realized that some processors require objects to be aligned along 4-byte boundaries. What exactly does this mean, and which specific systems have alignment requirements? Suppose I have an arbitrary pointer: unsigned char* ptr Now, I'm trying to retrieve a double value from a memory location: double d = **((double*)ptr); Is this going to cause problems? 回答1: It can definitely cause

Alignment along 4-byte boundaries

由 喜你入骨 提交于 2020-01-09 09:08:32
问题 I recently got thinking about alignment... It's something that we don't ordinarily have to consider, but I've realized that some processors require objects to be aligned along 4-byte boundaries. What exactly does this mean, and which specific systems have alignment requirements? Suppose I have an arbitrary pointer: unsigned char* ptr Now, I'm trying to retrieve a double value from a memory location: double d = **((double*)ptr); Is this going to cause problems? 回答1: It can definitely cause

How to read cpu frequency on android device [closed]

由 試著忘記壹切 提交于 2020-01-08 20:06:10
问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed last year . Is there any Java API for that? How can I read this information. 回答1: To have frequency on Android, just read these special files in /sys directory: #cat "/sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq" #cat "/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_min_freq" #cat "/sys/devices/system/cpu/cpu0/cpufreq

How do I monitor the computer's CPU, memory, and disk usage in Java?

由 ☆樱花仙子☆ 提交于 2020-01-08 09:33:13
问题 I would like to monitor the following system information in Java: Current CPU usage** (percent) Available memory* (free/total) Available disk space (free/total) *Note that I mean overall memory available to the whole system, not just the JVM. I'm looking for a cross-platform solution (Linux, Mac, and Windows) that doesn't rely on my own code calling external programs or using JNI. Although these are viable options, I would prefer not to maintain OS-specific code myself if someone already has

Java性能优化——操作系统性能监控

由 巧了我就是萌 提交于 2020-01-07 17:49:35
【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 1.CPU使用率 总述 CPU使用率可以分为 用户态CPU使用率 和 系统态CPU使用率 。 用户态CPU使用率 ：应用程序代码所执行的时间占CPU总执行时间的百分比。 系统态CPU使用率 ：应用程序调用操作系统代码所执行的时间占CPU总时间的百分比。如果较高，说明有共享资源的竞争或者大量IO交互操作。 减少系统态CPU使用率，将CPU更多的执行时间分配到应用程序本身，可以提高应用性能。 PS：要提升性能，除了CPU使用率，还要监控单位时间内执行的指令数、每条执行所需的周期等，防止等待状态也被当成了高效执行。 Windows监控CPU使用率 使用任务管理器进行监控。 左上角是CPU使用率总和，右上角是每个CPU的使用率，绿色代表每个CPU使用率，红色代表每个CPU的系统态使用率，前后两者的差代表用户态使用率。 2.CPU调度程序运行队列 总述 CPU调度程序运行队列就是那些已经准备好运行、正在等待可用CPU来执行他们的线程。 虚拟处理器个数 = Runtime.getRuntime().availableProcessors() 当队列长度达到虚拟处理器个数的3-4倍时，就需要注意或者进行优化了。 对于上述情况有两种解决措施： 增加CPU 对应用程序的算法进行优化来改进CPU使用率。如减少垃圾回收的频率

java性能监控常用的几个命令

由 假如想象 提交于 2020-01-07 17:48:18
【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 找到性能问题的第一步是监控应用的行为，通过监控提供的线索，我们可以将性能问题进行归类并分析。 1、CPU使用率：大多数操作系统的CPU使用率分为用户态CPU使用率和系统态CPU使用率。用户态CPU使用率是指执行应用程序代码的时间占总CPU时间的百分比，相比而言，系统态CPU使用率是指应用执行操作系统调用的时间占总CPU时间的百分比。系统态CPU使用率高意味着共享资源有竞争或者I/O设备之间有大量的交互。理想情况下，应用达到最高性能和扩展时，它的系统态CPU使用率为0%，所以提高应用性能和扩展性的一个目标是尽可能降低系统态CPU使用率。 CPU停滞通常会浪费几百个时钟周期，因此提高计算密集型应用性能的策略是减少停滞或者改善CPU高速缓存使用率，从而减少CPU在等待内存数据时浪费的时钟周期。 Linux命令行监控CPU使用率的有vmstat或者top（或者htop，需要自行安装，但查看效果更好）： vmstat 采集间隔(秒) 采集次数 当一直监控时，可以省去采集次数，即 vmstat 2，每隔2秒采集一次，一直持续。 命令介绍完毕，现在开始实战讲解每个参数的意思，后面还会使用到： r 表示运行队列的长度，值是运行队列中轻量级进程的实际数量，即当内核线程已经准备好运行只是还没有可用的处理器执行时，运行队列就会有值。

What is the most efficient way to scrape multiple single and branch OIDs?

由 好久不见. 提交于 2020-01-07 05:47:09
问题 I am always in a war between maximum speed and minimal resource consumption, so my goal is to find the best combination for speed and resource consumption. For each snmp device I would like to scan the oids under several branches. Each branch has a dynamic amount of oids under it so i don't know what specific oids i need, I just know that I need all oids under a branch. I have some devices that only support SNMPv1 so for those devices I write code that is compatible with SNMPv1. For the rest
订阅 cpu