Re: [RFC v1 0/1] nvme testsuite runtime optimization

[Sagi Grimberg]

> > > > While testing the fc transport I got a bit tired of wait for the I/O jobs to
> > > > finish. Thus here some runtime optimization.
> > > >
> > > > With a small/slow VM I got following values:
> > > >
> > > > with 'optimizations'
> > > >      loop:
> > > >        real    4m43.981s
> > > >        user    0m17.754s
> > > >        sys     2m6.249s
> >
> > How come loop is doubling the time with this patch?
> > ratio is not the same before and after.
>
> first run was with loop, second one with rdma:
>
> nvme/002 (create many subsystems and test discovery)         [not run]
>      runtime  82.089s  ...
>      nvme_trtype=rdma is not supported in this test
>
> nvme/016 (create/delete many NVMeOF block device-backed ns and test discovery) [not run]
>      runtime  39.948s  ...
>      nvme_trtype=rdma is not supported in this test
> nvme/017 (create/delete many file-ns and test discovery)     [not run]
>      runtime  40.237s  ...
>
> nvme/047 (test different queue types for fabric transports)  [passed]
>      runtime    ...  13.580s
> nvme/048 (Test queue count changes on reconnect)             [passed]
>      runtime    ...  6.287s
>
> 82 + 40 + 40 - 14 - 6 = 142. So loop runs additional tests. Hmm, though my
> optimization didn't work there...

How come loop is 4m+ while the others are 2m+ when before all
were the same timeframe more or less?

> > > Those jobs are meant to be run for at least 1G to establish
> > > confidence on the data set and the system under test since SSDs
> > > are in TBs nowadays and we don't even get anywhere close to that,
> > > with your suggestion we are going even lower ...
> >
> > Where does the 1G boundary coming from?
>
> No idea, it just the existing hard coded values. I guess it might be from
> efa06fcf3c83 ("loop: test partition scanning") which was the first real test
> case (according the logs).

Was asking Chaitanya why is 1G considered sufficient vs. other sizes?
Why not 10G? Why not 100M?