Messages in this thread | | | From | Gene Heskett <> | Subject | Re: USB making time drift [was Re: dynamic-hz] | Date | Wed, 15 Dec 2004 11:44:38 -0500 |
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On Wednesday 15 December 2004 04:17, Andrea Arcangeli wrote: >On Tue, Dec 14, 2004 at 09:59:23PM -0500, Gene Heskett wrote: >> Which way? I was running quite fast here, several minutes an > >In the future, if I disable the logic it goes in the past at the > same speed it was previously going in the future. > >> hour, then I discovered the tickadj command, found its default >> was 10000, and started reducing it. At 9926, I'm staying within >> a sec an hour now. I have no idea when this started, I didn't > >That seems quite an hack, note I did an hack too and it make the > drift much smaller (it gets manageable). But our modifications are > wrong. > >The point is that this didn't happen with HZ=100, so it's not that >tickadj is wrong, it's the tick adjustment code that doesn't work. > The HZ=1000 is the culprit?
>You may want to recompile your kernel with HZ=100 and verify it goes >away (I didn't verify myself, but I verified the max irq latency I > get is 4msec, and in turn I'm sure HZ=100 would fix it
Humm, that might also reduce the obviousness of the irq activity in the audio, there are times when I can hear it very plainly while a low level audio src is in use, like the sub-millivolt levels that come out of my Hauppauge WinTV-GO+FM card. I keep having to turn the master down to almost zip in order to keep it from sounding like I have mice chewing in the walls, but its coming from the speakers. Onboard AC-97 audio of course. Crappy stuff... Humm, 100HZ would translate to 10 millisecond intervals. If you had a 4 millisecond latency, that would be spread over 4 of the 1000 hz interrupts. That sounds rather confusing to the service routine I imagine.
I'll do that just for grins & report back.
-- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) 99.30% setiathome rank, not too shabby for a WV hillbilly Yahoo.com attorneys please note, additions to this message by Gene Heskett are: Copyright 2004 by Maurice Eugene Heskett, all rights reserved.
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