Changing p_swtime and td_slptime to ticks
jroberson at chesapeake.net
Tue Sep 18 14:20:15 PDT 2007
On Tue, 18 Sep 2007, Andre Oppermann wrote:
> Jeff Roberson wrote:
>> On Mon, 17 Sep 2007, Julian Elischer wrote:
>>> Jeff Roberson wrote:
>>>> Enclosed is a patch that fixes swapping with ULE. ULE has never properly
>>>> set p_swtime and td_slptime which are used by the swapout/swapin code to
>>>> select the appropriate thread to swap.
>>> I have not looked at in the depth required, but 2 points that I was unable
>>> to check to my satisfaction before I got called away for work....
>>> 1/ the source of the ticks is a monotonically increasing count that never
>>> goes backwards or changes?
>> ticks is incremented each time hardclock() is called. That's it.
>>> 2/ nothing that used to be accounted in seconds becomes accounted for in
>> I scale back to seconds where it is required. Really I think ticks would
>> be the better metric in vm_glue.c but didn't want to make any drastic
> ticks is 2^31 on x86 and at HZ=1000 is wraps within a reasonable
> short uptime. You have to make sure that your code handles that
> correctly or you run into lots of strange effects which are almost
> impossible to reproduce. In TCP we've got bitten by that.
Thanks Andre, this is a good point. For the td_slptime I don't think it's
of practical concern. However, for swtime I think I will convert it then
to seconds from boot.
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