On Mon, 4 Dec 2006, Greg KH wrote:
> > You sent your original patch off to Linus instead of the variant I sent
> > in, even though your patch violates the locking rules (see the kerneldoc
> > for usb_new_device)!
>
> I did this as your variant was in the "this might possibly work but I'm
> not sure" type of patch :)
>
> Actually the main reason this went in is that a set of patches from you
> a while ago would only apply properly if my multi-threaded patch was
> also applied.
>
> So I moved it higher up in the patch queue and then forgot about it
> until right now, when you pointed out that it went into the tree...
Okay, that makes sense. I still think it should be removed or changed,
but now it looks like it's up to me to submit the patches...
> > By the way, have you observed any significant improvements in peformance
> > from this patch? I don't have any experience with systems having lots of
> > USB devices attached. For that matter, does speeding up khubd make any
> > significant change to the overall boot time for a system? One wouldn't
> > think the other boot-up steps would have to wait for khubd...
>
> No, I haven't, but I have not set up a large quantity of devices to test
> it with.
Hmm. If almost nobody is going to see any noteworthy improvement then
there doesn't seem to be much point in doing the parallel probing.
> If you want to port your old patch to apply on top of the tree right
> now, I'll be glad to consider it.
I am undecided. Here are the issues:
1. Will people have lots of devices hooked directly into a
root hub? If yes, then something like the patch I sent
before would be good (handle multiple ports on a single
hub in parallel).
2. Will people have lots of external hubs? If yes, then it
would be better to start up several khubd threads (handle
multiple hubs in parallel).
3. Would a combination of 1 & 2 be better than either alone?
4. Is the payoff too small? Maybe it would be best to do
nothing at all.
The only way to answer these questions is to find out what people are
currently doing. In my limited experience people usually have only a few
USB devices. Is there any way to find test cases where a large number of
devices are hooked up to a single computer?
Alan Stern
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