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    Subject[PATCH 13/15] perf_counter: rework the task clock software counter
    Rework the task clock software counter to use the context time instead
    of the task runtime clock, this removes the last such user.

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    ---
    kernel/perf_counter.c | 42 ++++++++++++------------------------------
    1 file changed, 12 insertions(+), 30 deletions(-)

    Index: linux-2.6/kernel/perf_counter.c
    ===================================================================
    --- linux-2.6.orig/kernel/perf_counter.c
    +++ linux-2.6/kernel/perf_counter.c
    @@ -974,9 +974,6 @@ int perf_counter_task_disable(void)
    curr_rq_lock_irq_save(&flags);
    cpu = smp_processor_id();

    - /* force the update of the task clock: */
    - __task_delta_exec(curr, 1);
    -
    perf_counter_task_sched_out(curr, cpu);

    spin_lock(&ctx->lock);
    @@ -1017,9 +1014,6 @@ int perf_counter_task_enable(void)
    curr_rq_lock_irq_save(&flags);
    cpu = smp_processor_id();

    - /* force the update of the task clock: */
    - __task_delta_exec(curr, 1);
    -
    perf_counter_task_sched_out(curr, cpu);

    spin_lock(&ctx->lock);
    @@ -2347,38 +2341,28 @@ static const struct hw_perf_counter_ops
    * Software counter: task time clock
    */

    -/*
    - * Called from within the scheduler:
    - */
    -static u64 task_clock_perf_counter_val(struct perf_counter *counter, int update)
    -{
    - struct task_struct *curr = counter->task;
    - u64 delta;
    -
    - delta = __task_delta_exec(curr, update);
    -
    - return curr->se.sum_exec_runtime + delta;
    -}
    -
    -static void task_clock_perf_counter_update(struct perf_counter *counter, u64 now)
    +static void task_clock_perf_counter_update(struct perf_counter *counter)
    {
    - u64 prev;
    + u64 prev, now;
    s64 delta;

    - prev = atomic64_read(&counter->hw.prev_count);
    -
    - atomic64_set(&counter->hw.prev_count, now);
    + update_context_time(counter->ctx);
    + now = counter->ctx->time;

    + prev = atomic64_xchg(&counter->hw.prev_count, now);
    delta = now - prev;
    -
    atomic64_add(delta, &counter->count);
    }

    static int task_clock_perf_counter_enable(struct perf_counter *counter)
    {
    struct hw_perf_counter *hwc = &counter->hw;
    + u64 now;
    +
    + update_context_time(counter->ctx);
    + now = counter->ctx->time;

    - atomic64_set(&hwc->prev_count, task_clock_perf_counter_val(counter, 0));
    + atomic64_set(&hwc->prev_count, now);
    hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
    hwc->hrtimer.function = perf_swcounter_hrtimer;
    if (hwc->irq_period) {
    @@ -2393,14 +2377,12 @@ static int task_clock_perf_counter_enabl
    static void task_clock_perf_counter_disable(struct perf_counter *counter)
    {
    hrtimer_cancel(&counter->hw.hrtimer);
    - task_clock_perf_counter_update(counter,
    - task_clock_perf_counter_val(counter, 0));
    + task_clock_perf_counter_update(counter);
    }

    static void task_clock_perf_counter_read(struct perf_counter *counter)
    {
    - task_clock_perf_counter_update(counter,
    - task_clock_perf_counter_val(counter, 1));
    + task_clock_perf_counter_update(counter);
    }

    static const struct hw_perf_counter_ops perf_ops_task_clock = {
    --



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