如何保证进程运行在特定的物理CPU核心和线程上？
这个问题询问如何确保两个进程在同一个 CPU 上运行。使用 sched_setaffinity 可以将进程限制为多个逻辑 CPU，但如何确保这些映射到特定的物理 CPU 和线程？
我期望映射为：
0 - CPU 0 线程 0
1 - CPU 0 线程 1
2 - CPU 1 线程 0
3 - CPU 1 线程 1
等等...
其中左侧的数字是 sched_setaffinity 中使用的相关 CPU。
然而，当我尝试测试这一点时，情况似乎不一定如此。
为了测试这一点，我使用了 CPUID 指令，该指令返回 EBX 中当前内核的初始 APIC ID：
void print_cpu()
{
int cpuid_out;
__asm__(
"cpuid;"
: "=b"(cpuid_out)
: "a"(1)
:);
std::cout << "I am running on cpu " << std::hex << (cpuid_out >> 24) << std::dec << std::endl;
}
然后我循环遍历 cpu 掩码中的位并设置它们一次一个，以便操作系统将进程依次迁移到每个逻辑CPU，然后我打印出当前的CPU。
这就是我得到的结果：
cpu mask is 0
I am running on cpu 0
cpu mask is 1
I am running on cpu 4
cpu mask is 2
I am running on cpu 2
cpu mask is 3
I am running on cpu 6
cpu mask is 4
I am running on cpu 1
cpu mask is 5
I am running on cpu 5
cpu mask is 6
I am running on cpu 3
cpu mask is 7
I am running on cpu 7
假设 CPU 根据我上面列出的方案分配初始 APIC ID，那么 cpu 掩码实际上并不对应于物理核心和线程。
如何找到 sched_setaffinity 掩码中位到物理内核的正确映射？
This question asks about ensuring two processes run on the same CPU. Using sched_setaffinity I can limit a process to a number of logical CPUs, but how can I ensure that these are mapped to specific physical CPUs and threads?
I expect that the mapping would be:
0 - CPU 0 thread 0
1 - CPU 0 thread 1
2 - CPU 1 thread 0
3 - CPU 1 thread 1
etc...
where the number on the left is the relevant CPU used in sched_setaffinity.
However, when I tried to test this, it appeared that this is not necessarily the case.
To test this, I used the CPUID instruction, which returns the initial APIC ID of the current core in EBX:
void print_cpu()
{
int cpuid_out;
__asm__(
"cpuid;"
: "=b"(cpuid_out)
: "a"(1)
:);
std::cout << "I am running on cpu " << std::hex << (cpuid_out >> 24) << std::dec << std::endl;
}
Then I looped over the bits in the cpu mask and set them one at a time so that the OS would migrate the process to each logical CPU in turn, and then I printed out the current CPU.
This is what I got:
cpu mask is 0
I am running on cpu 0
cpu mask is 1
I am running on cpu 4
cpu mask is 2
I am running on cpu 2
cpu mask is 3
I am running on cpu 6
cpu mask is 4
I am running on cpu 1
cpu mask is 5
I am running on cpu 5
cpu mask is 6
I am running on cpu 3
cpu mask is 7
I am running on cpu 7
assuming that the CPU assigns initial APIC IDs according to the scheme I listed above, it would seem that the cpu mask doesn't actually correspond to the physical core and thread.
How can I find the correct mapping of bits in the mask for sched_setaffinity to physical cores?
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hwloc 是一个可移植的 C 库，用于发现硬件/NUMA 拓扑，以及绑定进程/线程到特定的核心。它具有发现物理/逻辑核心，然后将进程/线程绑定到其上的功能。
它也看起来它也可以返回
cpu_set_t与sched_setaffinity()一起使用，如果您想继续直接使用它。hwloc is a portable C library for discovering hardware/NUMA topology, and also binding processes/threads to particular cores. It has functions to discover physical/logical cores, and then bind a process/thread to it.
It also looks like it can also return a
cpu_set_tfor use withsched_setaffinity(), if you want to keep using that directly.