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SubjectRe: jiffies rollover, uptime etc.
On Mon, 18 Feb 2002, Ben Greear wrote:

> I wonder, is it more expensive to write all drivers to handle the
> wraps than to take the long long increment hit? The increment is
> once every 10 miliseconds, right? That is not too often, all things
> considered...

If you are willing to code in assembler instead of C you can do better,
at least on x86. You just need to do a 32 bit increment on the LS word,
and if you get a carry you can incr the MS word.

> Maybe the non-atomicity of the long long increment is the problem?

I doubt it, the problem is that the software which expects jiffies is
not all going to work well 64 bit. I think that's more the issue, and why
Alan et al are fixing it piecemeal, I don't think there's some magic fix
they're missing.

> Does this problem still exist on 64-bit machines?

Absolutely. But not as often ;-)

--
bill davidsen <davidsen@tmr.com>
CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.

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