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SubjectRe: 2.6.20-rc6-mm3

* Karsten Wiese <> wrote:

> Similar weirdness here on rc6-mm2 and rc6-rt*: resume from disk waits
> unduly long.

i'm wondering whether the jiffies update fix from Thomas fixes this bug
for you.

If not then do you have a serial console enabled?

> Some waiting times from rc6-rt6 from memory:
> Config | HZ | NO_HZ + HRESTIMERS
> cmos clock unchanged | 2s | 6s
> cmos clock += 10min | | 2 minutes
> cmos clock += 2 month | 20s | > 4minutes, test interrupted

i've seen something like this on -rt (and incorrectly attributed it to
-rt) when running on a system which has a serial port and which has a
kernel console on that serial port. What happens is that after resume
(and straight after console suspend) every serial character printed
takes /alot/ of time - and resume does print a number of kernel messages
to the console. I didnt get any further in debugging this though, but
disabling the serial console made the problem go away.

a possibly related thing: the serial code is sensitive to jiffies
updates and timers, i saw that during early revisions of the dynticks
code - but the specifics escape me.

the slowdown could also be something like the kernel somehow wrapping
around jiffies and thus doing /alot/ of jiffy ticks? Or it could be a
miscalculation in the amount of jiffies that need updating, resulting in
a similar number of loops in the jiffy update code.

(i'll try to figure out this regression - but wanted to describe to you
the known things so far, maybe you'll figure it out faster than me.)

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