[time-nuts] time-nuts Digest, Vol 66, Issue 6

[Steve Rooke]

Under nix, I believe that running like this will result in the kernel
penalising the process by dropping it's priority as it is showing up
as a process hog. This isn't good for LH as it may not get the CPU
cycles when it actually needs them.

2010/1/4 Christopher Hoover <ch at murgatroid.com>:
> On 1/3/2010 5:53 PM, time-nuts-request at febo.com wrote:
>>
>> It's not an issue, except possibly vis-a-vis battery life in a laptop.
>>
>
> I haven't looked at the source code, but there are other concerns with the
> "while (true) { checkStuff(); Sleep(0); }" approach.
>
> According to the TFM, Sleep(0) is effectively a NOP when there are no other
> processes at that priorty ("If there are no other threads of equal priority
> ready to run, the function returns immediately, and the thread continues
> execution.").
>
> It also follow from the TFM that it will keep lower priority processes from
> running at all.
>
> For me, I'm most worried about behavior under virtualization -- this is
> unlikely to play nice under a VM  unless you choose a non-work conserving
> scheduler (which most people don't choose).

Are you thinking about running it inside a Windows VM on top of another OS?

> I would add that laptops are not the only machines these day that do
> effective power management.   This will likely keep your cores out of any
> P-states, and the higher power dissipation will keep fans running (higher).
>
> As I mentioned off list, a better approach, if it can be made to work with
> the current code structure, is select(2) or poll(2) (or one of the newer
> variants) on UN*X..   The equivalent, TTBOMK, for Win32 is
> WaitForMultipleObjects.    All of these leave the process unscheduled until
> there I/O is available or a timeout occurs.

Like what he said!

Steve Rooke

> -ch
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-- 
Steve Rooke - ZL3TUV & G8KVD
A man with one clock knows what time it is;
A man with two clocks is never quite sure.