On Fri, Jul 4, 2014 at 12:59 PM, Bart Van Assche <bvanassche@xxxxxxx> wrote: > > [...] the blk-iopoll framework defers work to softirq > context. This means that a context switch from interrupt to softirq > context has to occur before SRP completion processing can start. Recent > measurements on current hardware have shown that such a context switch > takes about 0.5 microseconds. Since I prefer to keep the latency of SRP > I/O as low as possible I haven't looked further into using blk-iopoll for the SRP initiator driver. Hi Bart, In the same manner that SoftirqD is the right place to process received packets in the networking space, it should be the case for IO completions in the storage space too. Note that typical packet latency in latest/fastest 10g NICs go below 5us when using NAPI so if we (== NIC drivers) are happy with the CS overhead there, we (== SCSI LLD storage drivers whose latency is in the area of 15-20us) should be happy here too. Specifically, the CS cost is amortized across multiple IOs. Or. -- 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
