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sched: restore deterministic CPU accounting on powerpc

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Since powerpc started using CONFIG_GENERIC_CLOCKEVENTS, the
deterministic CPU accounting (CONFIG_VIRT_CPU_ACCOUNTING) has been
broken on powerpc, because we end up counting user time twice: once in
timer_interrupt() and once in update_process_times().

This fixes the problem by pulling the code in update_process_times
that updates utime and stime into a separate function called
account_process_tick.  If CONFIG_VIRT_CPU_ACCOUNTING is not defined,
there is a version of account_process_tick in kernel/timer.c that
simply accounts a whole tick to either utime or stime as before.  If
CONFIG_VIRT_CPU_ACCOUNTING is defined, then arch code gets to
implement account_process_tick.

This also lets us simplify the s390 code a bit; it means that the s390
timer interrupt can now call update_process_times even when
CONFIG_VIRT_CPU_ACCOUNTING is turned on, and can just implement a
suitable account_process_tick().

account_process_tick() now takes the task_struct * as an argument.
Tested both with and without CONFIG_VIRT_CPU_ACCOUNTING.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Paul Mackerras 2007-11-09 22:39:38 +01:00 • committed by Ingo Molnar
parent 9a41785cc4
commit fa13a5a1f2
6 changed files with 18 additions and 43 deletions
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2
arch/powerpc/kernel/process.c
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@ -350,7 +350,7 @@ struct task_struct *__switch_to(struct task_struct *prev,
local_irq_save(flags);
account_system_vtime(current);
account_process_vtime(current);
account_process_tick(current, 0);
calculate_steal_time();
last = _switch(old_thread, new_thread);