Re: USB umass hard drive "failed to create xfers" when attaching

[Greg Troxel <gdt%lexort.com@localhost>]

Paul Goyette <paul%whooppee.com@localhost> writes:

> First, this is on a amd64 system, witwh 8core/16thread and 128GB of RAM.
>
> On IRC it was suggested (thanks, maya!) that the error message might be
> related to memory fragmentation.  I didn't believe it (given how much
> RAM I have), but a quick check with top(1) showed that I had more than
> 100GB of 'file cache' active.  So, I unmounted all my development trees
> (to force the cache to get flushed).  Sure enough, I am now able to
> successfully mount the USB drive!
>
> So, sounds like "something somewhere isn't quite right (tm)".  I would
> have expected a memory allocation failure to automatically trigger some
> mechanism to reclaim some of the file cache...

I have seen this too, on ehci.

My impression is that something, perhaps more umass than *hci, needs a
very large chunk of memory.  The system can end up with lots of memory
available, but not one large enough.  If the available memory in bytes
is enough, that may not trigger reclaiming.

My fuzzy impression is that the standard wisdom is that drivers should
not demand really large continuous chunks.