Messages in this thread | | | Date | Sat, 07 Aug 2004 13:21:11 -0600 | From | Robert Hancock <> | Subject | Re: ide-cs using 100% CPU |
| |
It isn't that the CPU is doing so much work, it's mostly waiting. However with this type of PIO access, the CPU must do all the reads/writes from the buffer and while doing this the CPU is blocked and cannot do anything else.
----- Original Message ----- From: "Hamie" <hamish@travellingkiwi.com> Newsgroups: fa.linux.kernel To: "Russell King" <rmk+lkml@arm.linux.org.uk> Cc: <linux-kernel@vger.kernel.org> Sent: Friday, August 06, 2004 1:46 PM Subject: Re: ide-cs using 100% CPU
> Russell King wrote: > > >On Sun, Jul 18, 2004 at 10:30:16AM +0100, Hamie wrote: > > > > > >>Anyone know why this happens? Something busy waiting? (BUt that should > >>show as system cpu right?) or something taking out really long locks? > >> > >> > > > >It'll be because IDE is using PIO to access the CF card, which could > >have long access times (so reading a block of sectors could take some > >time _and_ use CPU.) Obviously, PIO requires the use of the CPU, so > >the CPU can't be handed off to some other task while this is occuring. > > > > > > > Well... I did consider that. And not to disbelieve you, since you know > the kernel way better than I do, But decided I was being silly that a > 1.6GHz Pentium-M processor should use 100% CPU moving a couple of > MB/second across a CF interface... > > Is 100% CPU not excessive? IIRC my PIII-750 used to use less CPU doing > the same job as quick, or even slightly faster... > > And should it not use system CPU rather than user CPU? > > TIA > Hamish. > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |