[measurement] (was Re: XF4 (mach64) help please)

Iain Sandoe iain at sandoe.co.uk
Fri Apr 20 21:01:07 EST 2001

I wrote:
> On  Thu, Apr 19, 2001, Geert Uytterhoeven wrote:
>> On Thu, 19 Apr 2001, Iain Sandoe wrote:
>>> On Thu, Apr 19, 2001,  Ani Joshi wrote:
>>> > On Thu, 19 Apr 2001, William Blew wrote:
>>> >> On Thu, 19 Apr 2001, Iain Sandoe wrote:
>>> >> > 2/  how difficult would it be to plumb the scroll acceleration back
>>> the
>>> >> > console driver?  (would one need access to the NDA stuff?) -- the
> scrolling
>>> >> > of console is a real problem in blocking sound :-/
>>> >>
>>> >> For mach64 at least, I would start by porting the CopyScreen2Screen XXA
>>> >> operation into the kernel and then using it during scrolling.
>>> >
>>> > This is already done by atyfb in the kernel,
>>> then why is the atyfb scroll (and fbdevhw) _so_ much slower than the X
>>> 'native' driver ... the same reason as below?
>> Because xterm uses jump scroll? Try scrolling line by line in X11.
> hmmm.  I was comparing "before" and "after" changing to Ani's new ati_drv.o
> (before was using libfbdevhw.a) - in all other respects the configuration
> was identical.
> this is mach64 (3DU Pro) on G3/beige - the difference seemed to be striking
> enough to comment (but I guess I could wind it back and do an X11Perf).

       with libfbdevhw.a           with new ati_drv.o/atimisc_drv.o

-scroll500    51.8/sec                76.5/sec
-shmput500    14.2/sec                25.4/sec

doesn't seem that different, I suppose, but this is...

cat test.txt  10.382 sec               5.132 sec

I guess that's what I've noticed on things like kernel builds.

>>> >however the problem lies in
>>> > the entire fbcon layer where there is some improper locking/interrupts
>> Read: the entire console layer. Fbcon cannot (read: couldn't) use interrupts
>> because the upper console layer disables (disabled) interrupts.
>>> > going on there.  This was discussed here and on linux-fbdev a few months
>>> > ago and I believe will be addressed in 2.5.
>>> and there is a (temporary) fix for it (I believe) involving a patch from
>>> Andrew Morton - (which I haven't had time to try on PPC yet).  Will that fix
>>> the slow console scroll as well?
>> It's supposed to. Haven't tried it yet, though.
> I will ASAP - AFAICT the various blocking issues are the main problem with
> (pmac) sound now.

I've fetched AM's latest console patch (2.4.3-pre8) and will try applying it
later and re-run the libfbdevhw.a test.


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