> On Aug 29, 2018, at 11:49 AM, w.kruzel via openzfs-developer
> <developer@lists.open-zfs.org> wrote:
>
> I think yes, there is sufficient demand to have I/O at such level. What do
> you mean by higher rate for the same workload? If types of devices - I have
> tested two Intel nvme disks and one of them had a throughput limit on 1
> thread at about 225MB/s while the other had an output of 285MB/s
> I shall provide the flamegraphs tomorrow.
> But I see a pattern between single threaded reads from NVME and multi
> threaded reads.
It is usually easy to see the I/Os to a device and see how many are queued
there.
I don't run FreeNAS or *BSD, but I'd be surprised if "iostat -x" doesn't show
the queue
depth. Alternatively, iosnoop can show exactly when I/Os are scheduled and
completed
so it is easy to observe overlaps.
Now measurements at the disk won't prove that the I/O is multithreaded, but it
can
disprove that the I/O is single-threaded.
-- richard
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