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.

> >     rdma:
> >       real    2m35.160s
> >       user    0m6.264s
> >       sys     0m56.230s
> >
> >     tcp:
> >       real    2m30.391s
> >       user    0m5.770s
> >       sys     0m46.007s
> >
> >     fc:
> >       real    2m19.738s
> >       user    0m6.012s
> >       sys     0m42.201s
> >
> > base:
> >     loop:
> >       real    7m35.061s
> >       user    0m23.493s
> >       sys     2m54.866s
> >
> >     rdma:
> >       real    8m29.347s
> >       user    0m13.078s
> >       sys     1m53.158s
> >
> >     tcp:
> >       real    8m11.357s
> >       user    0m13.033s
> >       sys     2m43.156s
> >
> >     fc:
> >       real    5m46.615s
> >       user    0m12.819s
> >       sys     1m46.338s
>
> 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?

> we cannot change the dataset size for slow VMs, instead add
> a command line argument and pass it to tests e.g.
> nvme_verification_size=XXX similar to nvme_trtype but don't change
> the default values which we have been testing for years now
>
> Testing is supposed to be time consuming especially verification jobs..

I like the idea, but I think it may need to be the other way around.
Have shortest possible runs by default.