re: kern/19803 (usbd_alloc_buffer fails often)

[matthew green <mrg%eterna.com.au@localhost>]

> State-Changed-From-To: open->closed
> State-Changed-By: maya%NetBSD.org@localhost
> State-Changed-When: Mon, 05 Aug 2019 22:13:36 +0000
> State-Changed-Why:
> This PR documents an issue but:
> - Is stale, so likely to be ignored,
> - Doesn't contain the right information.
> 
> This is likely a memory fragmentation issue. I am under the impression USB still uses
> more contiguous memory than it absolutely has to, so perhaps we could use a reminder,
> but this PR isn't a good reminder because it doesn't talk about it.
> 
> Memory fragmentation issues have come and gone in netbsd since the filing of this PR,
> so perhaps things are better or worse now. It's unclear.

AFAICT, this problem is still 100% the same.

now that your update talks about fragmentation, i think the
PR has all the details it needs -- it certainly happens on
a 64GB machine with a lot of free ram that was active in
recent times.  enough concurrent 4095mb dd's ends up making
it work again.

unless the problem is documented in another PR, i think this
one should be re-opened.


.mrg.