If I'm using a test like this:
... how frequently is the condition retested? Once every second?
Is is possible that having dozens of such tests all running at the same time could slow things down? Should I write my own loop that tests every 10 seconds instead?
It is possible but not very likely given that Pause Until has this setting to reduce the CPU burden (shown off here):
I don't think anything one can "write" using a collection of KM actions would be more efficient than something built into KM in the first place.
I may be wrong...
BTW, the calculation you're using will always be non-zero except when UPTIME() is exactly 90.
I think the test you should use is UPTIME() > 90
I understand your rationale. I'm trying to come up with a counter-example, but cannot. However it should be possible to rewrite the macro to "trigger" once per second instead of pausing in some sort of loop. But even so, I doubt if that would make much difference.
It might be worth knowing how exactly the "Reduce CPU usage" works. I thought that I read a post which said that it "tapers off" execution after different durations (1 min, 5 min, etc.)
Before I posted earlier I searched for more info on that without success and then continued on the basis of what should be common sense. But I can't honestly say that @August's idea is without merit until he tries it 
He should probably try it with a more computationally heavy operation than a simple math test, perhaps something like this:
And he would probably have to conduct this test over a long period of time, while logging the CPU usage over that time frame. Not easy. But he's an experimenter and a hard worker.
You're probably right, but here's a very simple test I left running on my computer while heading to the gym:
Pause Until — How Frequently does it evaluate (with reduce CPU usage enabled).kmmacros (22 KB)
Test completed in 88:35 minutes
Pause_______"Error"_______CPU
1 ms_______2 ms_______72.9%
1 ms_______2 ms_______109.2%
1 ms_______2 ms_______107.9%
1 ms_______2 ms_______108.9%
1 ms_______2 ms_______91.5%
2 ms_______21 ms_______98.3%
2 ms_______22 ms_______79.8%
2 ms_______22 ms_______81%
2 ms_______1 ms_______81%
2 ms_______22 ms_______128.1%
4 ms_______19 ms_______102.5%
4 ms_______20 ms_______100.8%
4 ms_______20 ms_______85%
4 ms_______20 ms_______73.4%
4 ms_______20 ms_______67.6%
8 ms_______15 ms_______66.7%
8 ms_______16 ms_______61.2%
8 ms_______16 ms_______61%
8 ms_______16 ms_______60.5%
8 ms_______1 ms_______51.4%
16 ms_______7 ms_______47%
16 ms_______8 ms_______41.3%
16 ms_______8 ms_______45.6%
16 ms_______8 ms_______46.1%
16 ms_______8 ms_______60.9%
32 ms_______12 ms_______56.6%
32 ms_______13 ms_______60.7%
32 ms_______13 ms_______54.3%
32 ms_______13 ms_______48.4%
32 ms_______13 ms_______43.5%
64 ms_______1 ms_______38.5%
64 ms_______2 ms_______34.8%
64 ms_______2 ms_______37.8%
64 ms_______2 ms_______44.9%
64 ms_______2 ms_______47.8%
128 ms_______21 ms_______45.3%
128 ms_______2 ms_______36.8%
128 ms_______22 ms_______30.2%
128 ms_______1 ms_______40.6%
128 ms_______15 ms_______96.5%
256 ms_______19 ms_______54.9%
256 ms_______20 ms_______73.1%
256 ms_______20 ms_______59.3%
256 ms_______20 ms_______138.5%
256 ms_______20 ms_______150.1%
512 ms_______15 ms_______78.6%
512 ms_______16 ms_______47.2%
512 ms_______16 ms_______31.1%
512 ms_______16 ms_______69.8%
512 ms_______16 ms_______46%
1024 ms_______7 ms_______64.1%
1024 ms_______8 ms_______74.8%
1024 ms_______8 ms_______67.2%
1024 ms_______7 ms_______158.1%
1024 ms_______16 ms_______119.8%
2048 ms_______12 ms_______45.6%
2048 ms_______18 ms_______153.8%
2048 ms_______6 ms_______30.5%
2048 ms_______16 ms_______32.4%
2048 ms_______11 ms_______53.4%
4096 ms_______6 ms_______39.4%
4096 ms_______5 ms_______45.3%
4096 ms_______11 ms_______37.5%
4096 ms_______2 ms_______31.3%
4096 ms_______8 ms_______31.8%
8192 ms_______21 ms_______108.6%
8192 ms_______12 ms_______37.3%
8192 ms_______2 ms_______33.1%
8192 ms_______11 ms_______119.9%
8192 ms_______9 ms_______33%
16384 ms_______134 ms_______32.3%
16384 ms_______140 ms_______34.1%
16384 ms_______146 ms_______106.8%
16384 ms_______155 ms_______69.2%
16384 ms_______149 ms_______57%
32768 ms_______297 ms_______28.5%
32768 ms_______290 ms_______35.6%
32768 ms_______294 ms_______32.6%
32768 ms_______280 ms_______35.3%
32768 ms_______288 ms_______27.1%
65536 ms_______4574 ms_______29.2%
65536 ms_______4586 ms_______40.9%
65536 ms_______4589 ms_______37.1%
65536 ms_______4595 ms_______39.1%
65536 ms_______4586 ms_______34.2%
131072 ms_______4062 ms_______73.4%
131072 ms_______4064 ms_______34.6%
131072 ms_______4063 ms_______42.1%
131072 ms_______4064 ms_______31.3%
131072 ms_______4060 ms_______33.4%
262144 ms_______304 ms_______38.7%
262144 ms_______3016 ms_______42.1%
262144 ms_______3018 ms_______33.1%
262144 ms_______3016 ms_______100%
262144 ms_______3023 ms_______126.6%
524288 ms_______929 ms_______30%
524288 ms_______932 ms_______120.1%
524288 ms_______951 ms_______39%
524288 ms_______939 ms_______36.5%
524288 ms_______922 ms_______45.5%
Nothing conclusive (of course, the way this test is set up), but the data seems to indicate that the Pause Until (with reduce CPU usage enabled) slows down evaluation frequency after about 10 seconds of reevaluating the conditions, and then again even more so after about a minute.
Great work. I wish KM had some built-in charting actions for situations like this.
OOPS! Thanks! Fingers sometimes don't match my brain.
Thanks @tiffle, that's what I needed to know. I'll keep that setting on and not worry about it. I only expect to have at most a couple of dozen running at once, waiting for bootup processes to complete.
Test it and see? Maybe with Activity Monitor open as well?
Here's a macro that'll spawn 20 "Pause until..." macros that replicate yours, run the system_profiler shell command, kill all the "Pause until..." macros, run the shell command again. There's a "beep" halfway through if you want to check the KM menu bar item to see the pauses are running (before the beep) or cancelled (after).
Pause test.kmmacros (7.8 KB)
Results for 5 runs:
So anything from 7 seconds (~15%) slower to > 1 second faster with pauses, suggesting that there's a small slow down but that other background activity is just as important. This is with "Reduce CPU Usage" off and the un-paused shell script done second so it would benefit from any cacheing, so the un-paused section has every advantage.
I suspect that you'll see even less impact in real world use, especially if this is for your startup macro where the pauses will impact CPU use but most of your macro's actions (launching apps) are I/O bound and any CPU use is probably on other cores anyway.
