自旋锁在单处理器单核体系结构中有用吗? [英] Is spin lock useful in a single processor uni core architecture?
问题描述
我对自旋锁的功能感到困惑.
I am confused by the function of spin lock.
自旋锁用于阻止进程重新调度. 但是，在一台只有一个内核的机器中，使用自旋锁是否有用 防止上下文切换?
The spin lock is used to stop the process from re-scheduling. However, in a machine with just one core, is it useful to use spin lock to prevent context switching?
推荐答案
简短答案:否.
根据 http://uw714doc. sco.com/en/man/html.3synch/Intro.3synch.html
According to http://uw714doc.sco.com/en/man/html.3synch/Intro.3synch.html
自旋锁不得在单处理器系统上使用.最好的情况是，单个处理器系统上的自旋锁会浪费资源，从而减慢锁的所有者.在最坏的情况下，它将使处理器死锁.
Spin locks must not be used on a single processor system. In the best case, a spin lock on a single processor system will waste resources, slowing down the owner of the lock; in the worst case, it will deadlock the processor.
From: http://blogs.microsoft.co.il/blogs/sasha/archive/2008/08/10/practical-concurrency-patterns-spinlock.aspx
在单处理器系统上，不需要自旋锁，因为仅在高IRQL上需要自旋锁同步.在较高的IRQL(高于调度IRQL)上，不会发生上下文切换，因此，除了旋转获取线程之外，还可以简单地在相关的IRQL上请求中断并返回；该中断将被屏蔽，直到释放线程将IRQL降低到所请求的IRQL以下为止.
On single-processor systems, spinlocks are not needed because spinlock synchronization is required on high IRQLs only. On high IRQLs (above dispatch IRQL) a context switch cannot occur, so instead of spinning the acquiring thread can simply request an interrupt on the relevant IRQL and return; the interrupt will be masked until the releasing thread lowers the IRQL below the requested IRQL.
对于单处理器系统，内核将忽略旋转计数值，并将其视为零-本质上将旋转锁设为无操作.
For single processor systems, the kernel will ignore the spin count value, and treat it as zero - essentially making a spinlock a no-op.
是的，自旋锁可能有用，并且可以提高某些操作的效率.但是，通常应从互斥锁开始，如果分析表明它是瓶颈，则可能需要考虑使用自旋锁.
Yes, spin locks can be useful, and improve efficiency of some operations. However, generally you should start with a mutex, and if profiling show it to be a bottleneck, you may want to consider a spinlock.
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