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翻译完成 Linux FAQs with Answers--How to find out which CPU core a process is running on.md
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translation by strugglingyouth
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Linux FAQs with Answers--How to find out which CPU core a process is running on
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================================================================================
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> Question: I have a Linux process running on my multi-core processor system. How can I find out which CPU core the process is running on?
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When you run performance-critical HPC applications or network-heavy workload on [multi-core NUMA processors][1], CPU/memory affinity is one important factor to consider to maximize their performance. Scheduling closely related processes on the same NUMA node can reduce slow remote memory access. On processors like Intel's Sandy Bridge processor which has an integrated PCIe controller, you want to schedule network I/O workload on the same NUMA node as the NIC card to exploit PCI-to-CPU affinity.
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As part of performance tuning or troubleshooting, you may want to know on which CPU core (or NUMA node) a particular process is currently scheduled.
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Here are several ways to **find out which CPU core is a given Linux process or a thread is scheduled on**.
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### Method One ###
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If a process is explicitly pinned to a particular CPU core using commands like [taskset][2], you can find out the pinned CPU using the following taskset command:
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$ taskset -c -p <pid>
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For example, if the process you are interested in has PID 5357:
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$ taskset -c -p 5357
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pid 5357's current affinity list: 5
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The output says the process is pinned to CPU core 5.
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However, if you haven't explicitly pinned the process to any CPU core, you will get something like the following as the affinity list.
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pid 5357's current affinity list: 0-11
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The output indicates that the process can potentially be scheduled on any CPU core from 0 to 11. So in this case, taskset is not useful in identifying which CPU core the process is currently assigned to, and you should use other methods as described below.
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### Method Two ###
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The ps command can tell you the CPU ID each process/thread is currently assigned to (under "PSR" column).
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$ ps -o pid,psr,comm -p <pid>
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PID PSR COMMAND
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5357 10 prog
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The output says the process with PID 5357 (named "prog") is currently running on CPU core 10. If the process is not pinned, the PSR column can keep changing over time depending on where the kernel scheduler assigns the process.
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### Method Three ###
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The top command can also show the CPU assigned to a given process. First, launch top command with "p" option. Then press 'f' key, and add "Last used CPU" column to the display. The currently used CPU core will appear under "P" (or "PSR") column.
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$ top -p 5357
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Compared to ps command, the advantage of using top command is that you can continuously monitor how the assigned CPU changes over time.
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### Method Four ###
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Yet another method to check the currently used CPU of a process/thread is to use [htop command][3].
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Launch htop from the command line. Press <F2> key, go to "Columns", and add PROCESSOR under "Available Columns".
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The currently used CPU ID of each process will appear under "CPU" column.
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Note that all previous commands taskset, ps and top assign CPU core IDs 0, 1, 2, ..., N-1. However, htop assigns CPU core IDs starting from 1 (upto N).
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--------------------------------------------------------------------------------
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via: http://ask.xmodulo.com/cpu-core-process-is-running.html
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作者：[Dan Nanni][a]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]:http://ask.xmodulo.com/author/nanni
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[1]:http://xmodulo.com/identify-cpu-processor-architecture-linux.html
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[2]:http://xmodulo.com/run-program-process-specific-cpu-cores-linux.html
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[3]:http://ask.xmodulo.com/install-htop-centos-rhel.html
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Linux 有问必答--如何找出哪个 CPU 内核正在运行进程
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================================================================================
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>问题：我有个 Linux 进程运行在多核处理器系统上。怎样才能找出哪个 CPU 内核正在运行该进程？
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当你运行需要较高性能的 HPC 程序或非常消耗网络资源的程序在 [多核 NUMA 处理器上][1]，CPU/memory 的亲和力是限度其发挥最大性能的重要因素之一。在同一 NUMA 节点上调整程序的亲和力可以减少远程内存访问。像英特尔 Sandy Bridge 处理器，该处理器有一个集成的 PCIe 控制器，要调整同一 NUMA 节点的网络 I/O 负载可以使用 网卡控制 PCI 和 CPU 亲和力。
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由于性能优化和故障排除只是一部分，你可能想知道哪个 CPU 内核（或 NUMA 节点）被调度运行特定的进程。
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这里有几种方法可以 **找出哪个 CPU 内核被调度来运行 给定的 Linux 进程或线程**。
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### 方法一 ###
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如果一个进程明确的被固定到 CPU 的特定内核，如使用 [taskset][2] 命令，你可以使用 taskset 命令找出被固定的 CPU 内核：
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$ taskset -c -p <pid>
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例如, 如果你对 PID 5357 这个进程有兴趣:
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$ taskset -c -p 5357
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pid 5357's current affinity list: 5
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输出显示这个过程被固定在 CPU 内核 5。
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但是，如果你没有明确固定进程到任何 CPU 内核，你会得到类似下面的亲和力列表。
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pid 5357's current affinity list: 0-11
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输出表明，该进程可能会被安排在从0到11中的任何一个 CPU 内核。在这种情况下，taskset 不会识别该进程当前被分配给哪个 CPU 内核，你应该使用如下所述的方法。
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### 方法二 ###
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ps 命令可以告诉你每个进程/线程目前分配到的 （在“PSR”列）CPU ID。
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$ ps -o pid,psr,comm -p <pid>
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PID PSR COMMAND
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5357 10 prog
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输出表示进程的 PID 为 5357（名为"prog"）目前在CPU 内核 10 上运行着。如果该过程没有被固定，PSR 列可以保持随着时间变化，内核可能调度该进程到不同位置。
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### 方法三 ###
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top 命令也可以显示 CPU 被分配给哪个进程。首先，在top 命令中使用“P”选项。然后按“f”键，显示中会出现 "Last used CPU" 列。目前使用的 CPU 内核将出现在 “P”（或“PSR”）列下。
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$ top -p 5357
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相比于 ps 命令，使用 top 命令的好处是，你可以连续监视随着时间的改变， CPU 是如何分配的。
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### 方法四 ###
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另一种来检查一个进程/线程当前使用的是哪个 CPU 内核的方法是使用 [htop 命令][3]。
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从命令行启动 htop。按 <F2> 键，进入"Columns"，在"Available Columns"下会添加 PROCESSOR。
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每个进程当前使用的 CPU ID 将出现在“CPU”列中。
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请注意，所有以前使用的命令 taskset，ps 和 top 分配CPU 内核的 IDs 为 0，1，2，...，N-1。然而，htop 分配 CPU 内核 IDs 从 1开始（直到 N）。
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--------------------------------------------------------------------------------
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via: http://ask.xmodulo.com/cpu-core-process-is-running.html
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作者：[Dan Nanni][a]
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译者：[strugglingyouth](https://github.com/strugglingyouth)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]:http://ask.xmodulo.com/author/nanni
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[1]:http://xmodulo.com/identify-cpu-processor-architecture-linux.html
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[2]:http://xmodulo.com/run-program-process-specific-cpu-cores-linux.html
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[3]:http://ask.xmodulo.com/install-htop-centos-rhel.html
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