Given what you just said it seems that an atomic op is better than first reading the cacheline and then incrementing a value in it right? Because if we first read then we acquire the cacheline in shared more. Later when we write to it we have to acquire it again in exclusive mode. The fetchadd would acquire the cacheline immediately in exclusive mode and thus save the acquisition in shared mode. > Yes, it is a one-direction barrier. > However, if there is not too many stuff in the OzQ, it has not too much > impact. It serializes prior accesses and has a simiar effect as an unlock operation. The processor cannot freely reorder instructions around the increment. That must have some sort of an impact on performance. > I still prefer the atomic operations. Noted. Andi: It seems that we can fall back on ia64 to an atomic operation without concern for performance. - : send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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