问题描述
这个问题询问有关确保两个进程在同一CPU上运行.使用sched_setaffinity，我可以将一个进程限制为多个逻辑CPU，但是如何确保将它们映射到特定的物理CPU和线程?
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?
我希望映射为:
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...
0 - CPU 0 thread 0
1 - CPU 0 thread 1
2 - CPU 1 thread 0
3 - CPU 1 thread 1
etc...
，其中左侧的数字是sched_setaffinity中使用的相关CPU.
where the number on the left is the relevant CPU used in sched_setaffinity.
但是，当我尝试对此进行测试时，似乎并不一定是这种情况.
However, when I tried to test this, it appeared that this is not necessarily the case.
为了测试这一点，我使用了CPUID指令，该指令返回了EBX中当前内核的初始APIC ID:
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;
}
然后，我循环遍历cpu掩码中的位，并一次将它们设置为1，以便操作系统将进程依次迁移到每个逻辑CPU，然后打印出当前的CPU.
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.
这就是我得到的:
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根据上面列出的方案分配了初始APIC ID，似乎cpu掩码实际上并不对应于物理内核和线程.
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.
如何找到sched_setaffinity的掩码中的位到物理核心的正确映射?
How can I find the correct mapping of bits in the mask for sched_setaffinity to physical cores?
推荐答案
hwloc 是一个便携式C库，用于发现硬件/NUMA拓扑，并将进程/线程绑定到特定的内核.它具有发现物理/逻辑核心，然后将进程/线程绑定到它的功能.
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.
看起来它也可以如果您想继续直接使用cpu_set_t，还可以返回cpu_set_t与sched_setaffinity()一起使用.
It also looks like it can also return a cpu_set_t for use with sched_setaffinity(), if you want to keep using that directly.
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