Re: AW: Slow I/O on USB media after commit f664a3cc17b7d0a2bc3b3ab96181e1029b0ec0e6

Finn Thain
2019-11-27T21:50:00Z

On Wed, 27 Nov 2019, Schmid, Carsten wrote:

> >
> > The sheer volume of testing (probably some terabytes by now) would
> > exercise the wear leveling algorithm in the FTL.
> >
> But with "old kernel" the copy operation still is "fast", as far as i
> understood. If FTL (e.g. wear leveling) would slow down, we would see
> that also in the old kernel, right?
>
> Andrea, can you confirm that the same device used with the old fast
> kernel is still fast today?

You seem to be saying we should optimize the kernel for a pathological
use-case merely because it used to be fast before the blk-mq conversion.
That makes no sense to me. I suppose you have information that I don't.

I assume that your employer (and the other corporations involved in this)
have plenty of regression test results from a variety of flash hardware to
show that the regression is real and the device is not pathological.

I'm not privy to any of that information so I will shut up and leave you
guys to it.

--

> > This in itself seems unlikely to improve performance significantly.
> > But if the flash memory came from a bad batch, perhaps it would have
> > that effect.
> >
> > To find out, someone may need to source another (genuine) Kingston
> > DataTraveller device.
> >