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[PATCH] sched: improve efficiency of sched_fork()

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Problem:
  sched_fork() has always called scheduler_tick() in some (unlikely)
  circumstances in order to update the current task in light of those
  circumstances.  It has always been the case that the work done by
  scheduler_tick() was more than was required to handle the problem in
  hand but no harm was done except for the waste of a few CPU cycles.

  However, the splitting of scheduler_tick() into two procedures in
  2.6.20-rc1 enables the wasted cycles to be saved as the new procedure
  task_running_tick() does all the work that is required to rectify the
  problem being handled.

Solution:
  Replace the call to scheduler_tick() in sched_fork() with a call to
  task_running_tick().

Signed-off-by: Peter Williams <pwil3058@bigpond.com.au>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Peter Williams 2006-12-19 12:48:50 +10:00 committed by Linus Torvalds
parent 136f1e7a8c
commit bc947631d1
1 changed files with 2 additions and 1 deletions
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3
kernel/sched.c
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@ -1567,6 +1567,7 @@ int fastcall wake_up_state(struct task_struct *p, unsigned int state)
return try_to_wake_up(p, state, 0); return try_to_wake_up(p, state, 0);
} }
static void task_running_tick(struct rq *rq, struct task_struct *p);
/* /*
* Perform scheduler related setup for a newly forked process p. * Perform scheduler related setup for a newly forked process p.
* p is forked by current. * p is forked by current.
@ -1627,7 +1628,7 @@ void fastcall sched_fork(struct task_struct *p, int clone_flags)
* runqueue lock is not a problem. * runqueue lock is not a problem.
*/ */
current->time_slice = 1; current->time_slice = 1;
scheduler_tick(); task_running_tick(cpu_rq(cpu), current);
} }
local_irq_enable(); local_irq_enable();
put_cpu(); put_cpu();