On Wed, Mar 12, 2025 at 01:34:02PM +1100, Dave Chinner wrote: > Wrong. > > Speculative non-blocking IO like NOWAIT is the wrong optimisation to > make for workloads that are very likely to block in the IO path. It > just adds overhead without adding any improvement in performance. Note that I suspect that most or at least many loop workloads are read-heavy. And at least for reads NOWAIT makes perfect sense. > Getting rid of the serialised IO submission problems that the loop > device current has will benefit *all* workloads that use the loop > device, not just those that are fully allocated. Yes, it won't quite > show the same performance as NOWAIT in that case, but it still > should give 90-95% of native performance for the static file case. > And it should also improve all the other cases, too, because now > they will only serialise when the backing file needs IO operations to > serialise (i.e. during allocation). And I agree that this should be a first step. > *cough* The whole ublk-zoned is a bit of a bullshit thing where Ming wrote up something that barely works to block inclusion of the zloop driver we really need for zoned xfs testing. Please don't take it serious.
