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SubjectRe: gettimeofday non-monotonic on 2.2.7 SMP
On Mon, 17 May 1999, dave madden wrote:

> =>From: Simon Kirby <sim@netnation.com>
> =>...
> =>My dual celeron 300As @ 450 MHz (2.2.9) running your program gives:
> =>
> =>Mon May 17 18:05:40 1999: fwd:774496/0:back max 0000000
> =>Mon May 17 18:05:41 1999: fwd:913473/0:back max 0000000
>
> That's what I expect, but what I get is:
>
> Mon May 17 18:57:17 1999: fwd:362637/4:back max 0000003
> Mon May 17 18:57:18 1999: fwd:866801/9:back max 0000003
> Mon May 17 18:57:19 1999: fwd:873531/7:back max 0000004
> Mon May 17 18:57:20 1999: fwd:872292/8:back max 0000003
> Mon May 17 18:57:21 1999: fwd:873949/9:back max 0000003
>
> with max [i.e. maximum clock decrement detected] going up to
> 5000-10000 (5-10ms) when I'm writing a CD or scrolling a Netscape
> window.

Just tried both (burning and scrolling in Netscape), no difference.

> Somebody else also reported success with a Dell SMP box running 2.2.9,
> so I compiled a copy for myself, but it didn't make any difference
> from 2.2.7.

Hmmm...

On loaded dual PII 350 at work:

Mon May 17 19:37:12 1999: fwd:279221/0:back max 0000000
Mon May 17 19:37:13 1999: fwd:596811/0:back max 0000000
Mon May 17 19:37:14 1999: fwd:670958/0:back max 0000000
Mon May 17 19:37:15 1999: fwd:678423/0:back max 0000000
Mon May 17 19:37:16 1999: fwd:647993/0:back max 0000000
Mon May 17 19:37:17 1999: fwd:672833/0:back max 0000000
Mon May 17 19:37:18 1999: fwd:665179/0:back max 0000000
Mon May 17 19:37:19 1999: fwd:638165/0:back max 0000000
Mon May 17 19:37:20 1999: fwd:624374/0:back max 0000000
Mon May 17 19:37:21 1999: fwd:675673/0:back max 0000000
Mon May 17 19:37:22 1999: fwd:651241/0:back max 0000000
Mon May 17 19:37:23 1999: fwd:682325/0:back max 0000000
Mon May 17 19:37:24 1999: fwd:639810/0:back max 0000000
Mon May 17 19:37:25 1999: fwd:627182/0:back max 0000000

Loaded dual PIII 450:

Mon May 17 19:38:09 1999: fwd:414354/0:back max 0000000
Mon May 17 19:38:10 1999: fwd:607775/0:back max 0000000
Mon May 17 19:38:11 1999: fwd:620345/0:back max 0000000
Mon May 17 19:38:12 1999: fwd:600607/0:back max 0000000
Mon May 17 19:38:13 1999: fwd:611782/0:back max 0000000
Mon May 17 19:38:14 1999: fwd:617592/0:back max 0000000
Mon May 17 19:38:15 1999: fwd:617667/0:back max 0000000
Mon May 17 19:38:16 1999: fwd:642869/0:back max 0000000
Mon May 17 19:38:17 1999: fwd:617755/0:back max 0000000
Mon May 17 19:38:18 1999: fwd:638355/0:back max 0000000
Mon May 17 19:38:19 1999: fwd:635935/0:back max 0000000

> =>Another thing..Perhaps try enabling "MTRR" in the kernel if it's not
> =>already to synchronize TSCs at bootup. I'm not sure if MTRR does this or
> =>not, actually, so maybe try flashing a new BIOS if all else fails. I know
> =>some BIOSes don't synchronize the TSCs properly, and this would confuse
> =>gettimeofday()...
>
> I'm using MTRR, but that code doesn't mention the TSC. My box is an
> Intel N440BX motherboard with the latest BIOS; what are your Celerons
> on?

All of the above (including my Celerons) are on ASUS P2B-DS boards. Don't
have any other boards...

Simon-

| Simon Kirby | Systems Administration |
| mailto:sim@netnation.com | NetNation Communications |
| http://www.netnation.com/ | Tech: (604) 684-6892 |


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