Messages in this thread | | | Date | Mon, 13 Dec 1999 14:31:27 +0100 | From | Marnix Coppens <> | Subject | Re: gettimeofday() a special case : why? |
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At 13:20 13/12/99 +0100, Artur Skawina wrote: >salkin@mindspring.com wrote: >> >> I don't want to be too OT or bothersome, but can someone explain why >> gettimeofday() is the one syscall that optimization at the ~100 cycle level >> makes sense for? If it's a long explanation, a link or pointer to a book is > >It's relatively common, used eg for timestamping events, often _every_ event >(strace a few X apps etc to see some examples). >It's also special because it does not need to switch domains -- on modern >cpus the required information is (or can be made) available to the caller, >hence it's possible to avoid entering the kernel at all. (in general, this >depends on cpu capabilities, security levels etc) >
Solaris for instance. If you run truss on an X app, you won't find gettimeofday(). The man pages also put gettimeofday() in section 3 iso. section 2. Interestingly enough, time() is still a syscall (section 2) and does show in truss. You'd think that time() is a special case of gettimeofday.
Marnix Coppens
--- Reality is that which | Artificial Intelligence when you stop believing | stands no chance against in it doesn't go away. (Philip K. Dick) | Natural Stupidity.
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