timers: split process wide cpu clocks/timers
Change the process wide cpu timers/clocks so that we: 1) don't mess up the kernel with too many threads, 2) don't have a per-cpu allocation for each process, 3) have no impact when not used. In order to accomplish this we're going to split it into two parts: - clocks; which can take all the time they want since they run from user context -- ie. sys_clock_gettime(CLOCK_PROCESS_CPUTIME_ID) - timers; which need constant time sampling but since they're explicity used, the user can pay the overhead. The clock readout will go back to a full sum of the thread group, while the timers will run of a global 'clock' that only runs when needed, so only programs that make use of the facility pay the price. Signed-off-by:Peter Zijlstra <a.p.zijlstra@chello.nl> Reviewed-by:
Ingo Molnar <mingo@elte.hu> Signed-off-by:
Ingo Molnar <mingo@elte.hu>
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32bd671d
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