Followup to: <20020410044243.2916.qmail@fastermail.com>
By author: "mark manning" <mark.manning@fastermail.com>
In newsgroup: linux.dev.kernel
>
> thanx - how much of a difference should i expect - i know the
> syscall is asking for at least the required ammount but that the
> task switcher might not give me control back for a while after the
> requested delay but i was expecting to be a little closer to what i
> had asked for - this isnt critical of corse but i would like to know
> what to expect.
>
Read the man page:
BUGS
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 speci
fied 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 mul
tiple 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.
-hpa
-- <hpa@transmeta.com> at work, <hpa@zytor.com> in private! "Unix gives you enough rope to shoot yourself in the foot." http://www.zytor.com/~hpa/puzzle.txt <amsp@zytor.com> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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