Hi everyone, I have a question regarding performance of RDMA atomic operations (i.e., compare-and-swap (CS) and fetch-and-add (FA)). I have been working on a project that requires data manipulation using RDMA atomic operations on 64-bit data objects. When I tested two scenarios: (1) multiple threads concurrently perform CS on data objects. each thread only touches objects it owns. each CS operation always succeeds. (2) multiple threads concurrently perform FA on data objects. each thread only touches objects it owns. each FA operation always succeeds. I expected (2) to perform better as I thought FA is faster operation than CS, but surprisingly (1) demonstrated better latency and throughput than (2) with about 10~20% margin. I measured the latency of each operation by calculating the time difference between making ibv_post_send() call and receiving its work completion via ibv_poll_cq(). Can CS be actually faster than FA? or could it be a hardware-specific issue (we have Mellanox HCAs in our cluster) or more likely to be an implementation problem of my own? Any help would be greatly appreciated and I am more than happy to provide any extra information necessary to answer this question. Thanks, Dong Young -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
