On Sun 2009-01-04 10:16:57, Linus Torvalds wrote: > > > On Sun, 4 Jan 2009, Arjan van de Ven wrote: > > > > To see this working, I uploaded a "before" and "after" kernel bootchart > > for one of my testboxes at > > > > http://www.fenrus.org/linux/before.svg > > http://www.fenrus.org/linux/after.svg > > Ok, so why does the serial port init take so long? That's a quarter of a > second for you, which is ridiculous. > > I _think_ it's the irq auto-probing, but that's just a guess. The 8250 > driver does some historical crud, like > > probe_irq_off(probe_irq_on()); > > to get rid of any pending irq's, but that should be entirely pointless > these days. I bet that line basically goes back to pre-history, before we > made the auto-probing much stabler. > > The irq auto-probing itself also has a few excessive delays, like waiting > for 0.1 s just to wait for spurious interrupts to trigger. Doing the extra > unnecessary probe makes that doubly expensive. > > Does this patch make any difference to you? I'm not at all sure that it's > the irq probing, but if it is, then this should make the serial probe go > much faster. Do serial ports even matter for the netbooks this is targeted at? Serial ports are gone even on normal notebooks and getting rare at desktop... > } > > /* forget possible initially masked and pending IRQ */ > - probe_irq_off(probe_irq_on()); Delete the comment, too? :-). -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
