Re: PATCH] incrase usbdevfs bulk buffer size
From: Pete Zaitcev
Date: Sun Oct 02 2005 - 17:10:16 EST
On Sat, 1 Oct 2005 16:20:59 -0400, Christopher Li <chrisl@xxxxxxxxxx> wrote:
> I hit this limit with running ehci in the VM. The a single ehci
> qTD transfer buffer can be 5 pages long, that is 20K. [...]
Even 16K is too much, IMHO.
> I can complicate the user space part to work around that,
> but it seems much simpler just allow usbdevfs to accept bigger buffers.
It seems, yes. However, I assure you that this is not going to
work for anyone who has anything reasonable swapped out, because
of the kmalloc().
16K is an order 2 allocation on systems with 4KB pages, such as
Opteron. It kinda sorta works, but not really.
This looks like a requirement to think about a better API. Also,
the things that Harald was trying to fix, with pids and signals,
just tell me that something was really wrong from the start.
-- Pete
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