On the other hand, setitimer could now be implemented with a POSIX
timer...
A question: Do most (any?) platforms have a way to get timer interrupts
at a finer resolution
than that used for the system clock (1 or 10ms if I understand
correctly). I ask this after
looking at the code in nanosleep where a real time task will wait in a
delay loop for any
nanosleep request for 2ms or less. This must really hurt context switch
times.
George
Robert de Vries wrote:
>
> This patch should not impact processes not using POSIX timers. The pointer
> to the array of POSIX timers is left NULL. Nothing is done. When the first
> timer is created and when a clone with the TIMER_CLONE flag is called, the
> timer overhead is created.
>
> As a reaction to the question if this should be in the kernel in the first
> place: IMHO, there is no way to emulate these calls in user space by using
> the setitimer() system call. For the following reasons:
>
> a. setitimer() sends only SIGALRM, POSIX timers can send any signal.
>
> b. setitimer() does not know about overruns, POSIX timers do.
>
> c. setitimer() can be used only once in a given process, you can have
> upto 32 (configurable) POSIX timers at the same time in your process.
>
> d. setitimer() cannot send extra information with its signal, POSIX timers
> can send a si_value when using RT signals.
>
> Any comments?
>
> Test code and some other patches can be found on:
> http://www.rhdv.cistron.nl/posix.html
>
> Robert
>
> ------------------------------------------------------------------------
> Name: 2.3.99-pre5.timer.patch
> 2.3.99-pre5.timer.patch Type: Plain Text (TEXT/PLAIN)
> Encoding: BASE64
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