November 28th, 2003


Things I never cared about until recently:



The current implementation of nanosleep is based on the normal kernel timer mechanism, which has a resolution of 1/HZ s (i.e, 10 ms on Linux/i386 and 1 ms on Linux/Alpha). Therefore, nanosleep pauses always for at least the specified time, however it can take up to 10 ms longer than specified until the process becomes runnable again. For the same reason, the value returned in case of a delivered signal in *rem is usually rounded to the next larger multiple of 1/HZ s.

As some applications require much more precise pauses (e.g., in order to control some time-critical hardware), nanosleep is also capable of short high-precision pauses. If the process is scheduled under a real-time policy like SCHED_FIFO or SCHED_RR, then pauses of up to 2 ms will be performed as busy waits with microsecond precision.



Got a test relay (R70-5D1-3) so I can start controlling 120VAC. It was only $2.30 or something. I'll need ~90. Hopefully if this one works I'll get them in bulk for much less.

Also picked up some more christmas lights... only $2.80 for 100 lights! (good thing, as I'll need 2048 lights... :-)) The christmas light packaging is confusing though: the box advertises low power all over, with the strand labeled 0.2A, but the box says each light is 100 mA....

eh. I'll play tomorrow.