On Thu, Sep 29, 2022 at 07:32:39PM +0300, Sagi Grimberg wrote: > > > > > 3. Do you have some performance numbers (we're touching the fast path > > > > here) ? > > > > > > This is pretty light-weight, accounting is per-cpu and only wrapped by > > > preemption disable. This is a very small price to pay for what we gain. > > > > It does add up, though, and some environments disable stats to skip the > > overhead. At a minimum, you need to add a check for blk_queue_io_stat() before > > assuming you need to account for stats. > > But QUEUE_FLAG_IO_STAT is set by nvme-mpath itself? > You mean disable IO stats in runtime? Yes, the user can disable it at any time. That actually makes things a bit tricky since it can be enabled at the start of an IO and disabled by the time it completes.
