原子指令可以跨越高速缓存行吗？
Can atomic instructions straddle cache lines?
像 LOCK DEC 这样的 x86 指令可以跨越多个缓存行，还是它们会出现段错误？
不问他们是否应该，只问是否允许。
（我知道某些 SSE 指令必须在缓存边界上对齐）
是的，这是允许的。您也可以尝试一下。或者阅读指令集参考：
The integrity of the LOCK prefix is not affected by the alignment of
the memory field. Memory locking is observed for arbitrarily
misaligned fields.
但另请参阅：
Exceptions
#AC(0) If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3.
请注意，通常不会启用对齐检查。
这是允许的，但您可能会出现性能大幅下降，因为锁可能无法在缓存内维护，并且可能会降级为完整的总线锁（实际上是完整的系统停顿）。
In the days of Intel 486 processors, the lock prefix used to assert a
lock on the bus along with a large hit in performance. Starting with
the Intel Pentium Pro architecture, the bus lock is transformed into a
cache lock. A lock will still be asserted on the bus in the most
modern architectures if the lock resides in uncacheable memory or if
the lock extends beyond a cache line boundary splitting cache lines.
Both of these scenarios are unlikely, so most lock prefixes will be
transformed into a cache lock which is much less expensive.
它可能因处理器规格而异，但请注意，另一个考虑因素是跨越线边界也可能意味着跨越页面边界，这更难维护（因此更有可能降级）。
像 LOCK DEC 这样的 x86 指令可以跨越多个缓存行，还是它们会出现段错误？
不问他们是否应该，只问是否允许。
（我知道某些 SSE 指令必须在缓存边界上对齐）
是的，这是允许的。您也可以尝试一下。或者阅读指令集参考：
The integrity of the LOCK prefix is not affected by the alignment of the memory field. Memory locking is observed for arbitrarily misaligned fields.
但另请参阅：
Exceptions
#AC(0) If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3.
请注意，通常不会启用对齐检查。
这是允许的，但您可能会出现性能大幅下降，因为锁可能无法在缓存内维护，并且可能会降级为完整的总线锁（实际上是完整的系统停顿）。
In the days of Intel 486 processors, the lock prefix used to assert a lock on the bus along with a large hit in performance. Starting with the Intel Pentium Pro architecture, the bus lock is transformed into a cache lock. A lock will still be asserted on the bus in the most modern architectures if the lock resides in uncacheable memory or if the lock extends beyond a cache line boundary splitting cache lines. Both of these scenarios are unlikely, so most lock prefixes will be transformed into a cache lock which is much less expensive.
它可能因处理器规格而异，但请注意，另一个考虑因素是跨越线边界也可能意味着跨越页面边界，这更难维护（因此更有可能降级）。