On Mon, Nov 16, 2015 at 5:46 PM, Tom Talpey <tom@xxxxxxxxxx> wrote: > On 11/15/2015 7:30 AM, Matan Barak wrote: >> >> This series adds support for completion timestamp. In order to >> support this feature, several extended verbs were implemented >> (as instructed in libibverbs). > > > Can you describe what these timestamps are actually for? It's not > clear at all from the comments. I'm assuming they are for some sort > of fine-grained statistics? Are they purely for userspace consumers? > > Completion timestamps could be used for various things. For examples, applications could use them for ordering (packet x came before packet y), measuring the delta (in raw cycles) between two packets (benchmarking) and between an event (for example, the call to ibv_post_send) and its respective WQE. The times are given in raw cycles time. The frequency of the respective timer is given in the extended verb of ibv_query_device, but this isn't system time just another form of raw time converted to nanoseconds. We currently implemented only the control path in kernel, so it's for userspace consumers only. However, implementing it in kernel shouldn't be hard. > -- > 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 -- 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
