[LAD] MIDI jitter - was: automation on Linux (modular approach)

[David Olofson]

On Thursday 25 March 2010, at 13.32.43, David Olofson <david at olofson.net> 
wrote:
> On Thursday 25 March 2010, at 12.49.31, Ralf Mardorf <ralf.mardorf at alice-
> dsl.net> wrote:
> [...]
> 
> > Btw. the
> > graphics has access to the main memory, unfortunately it's a shared RAM,
> > OTOH I used HPET so unwanted interrupts because of a shared RAM
> > shouldn't be the cause, if I do understand the workings of HR timers
> > correctly.
[...interrupts, DMA etc...]

BTW, the most common problem with graphics and realtime systems seems to be 
drivers abusing PCI port blocking as a performance hack. When the command 
buffer on the video card is full, the PCI bus blocks the CPU (completely - no 
IRQs, no nothing), instead of the driver going to sleep and waiting for an IRQ 
or some other proper solution. Might improve the 3D framerates slightly, but 
kills lowlatency audio...


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//David Olofson - Developer, Artist, Open Source Advocate

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