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    Subject[PATCH 27/37] vtime: Return nsecs instead of cputime_t to account
    Date
    Turn the full dynticks cputime clock source to return nsec while keeping
    its very internals jiffies based for performance reasons.

    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Michael Ellerman <mpe@ellerman.id.au>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Tony Luck <tony.luck@intel.com>
    Cc: Fenghua Yu <fenghua.yu@intel.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Stanislaw Gruszka <sgruszka@redhat.com>
    Cc: Wanpeng Li <wanpeng.li@hotmail.com>
    Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    ---
    kernel/sched/cputime.c | 31 +++++++++++--------------------
    1 file changed, 11 insertions(+), 20 deletions(-)

    diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
    index f3a56bf..2ecec3a 100644
    --- a/kernel/sched/cputime.c
    +++ b/kernel/sched/cputime.c
    @@ -678,20 +678,20 @@ void thread_group_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st)
    #endif /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */

    #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
    -static cputime_t vtime_delta(struct task_struct *tsk)
    +static u64 vtime_delta(struct task_struct *tsk)
    {
    unsigned long now = READ_ONCE(jiffies);

    if (time_before(now, (unsigned long)tsk->vtime_snap))
    return 0;

    - return jiffies_to_cputime(now - tsk->vtime_snap);
    + return jiffies_to_nsecs(now - tsk->vtime_snap);
    }

    -static cputime_t get_vtime_delta(struct task_struct *tsk)
    +static u64 get_vtime_delta(struct task_struct *tsk)
    {
    unsigned long now = READ_ONCE(jiffies);
    - cputime_t delta, other;
    + u64 delta, other;

    /*
    * Unlike tick based timing, vtime based timing never has lost
    @@ -700,7 +700,7 @@ static cputime_t get_vtime_delta(struct task_struct *tsk)
    * elapsed time. Limit account_other_time to prevent rounding
    * errors from causing elapsed vtime to go negative.
    */
    - delta = jiffies_to_cputime(now - tsk->vtime_snap);
    + delta = jiffies_to_nsecs(now - tsk->vtime_snap);
    other = account_other_time(delta);
    WARN_ON_ONCE(tsk->vtime_snap_whence == VTIME_INACTIVE);
    tsk->vtime_snap = now;
    @@ -710,9 +710,7 @@ static cputime_t get_vtime_delta(struct task_struct *tsk)

    static void __vtime_account_system(struct task_struct *tsk)
    {
    - cputime_t delta_cpu = get_vtime_delta(tsk);
    -
    - account_system_time(tsk, irq_count(), cputime_to_nsecs(delta_cpu));
    + account_system_time(tsk, irq_count(), get_vtime_delta(tsk));
    }

    void vtime_account_system(struct task_struct *tsk)
    @@ -727,15 +725,10 @@ void vtime_account_system(struct task_struct *tsk)

    void vtime_account_user(struct task_struct *tsk)
    {
    - cputime_t delta_cpu;
    -
    write_seqcount_begin(&tsk->vtime_seqcount);
    tsk->vtime_snap_whence = VTIME_SYS;
    - if (vtime_delta(tsk)) {
    - u64 nsecs;
    - delta_cpu = get_vtime_delta(tsk);
    - account_user_time(tsk, cputime_to_nsecs(delta_cpu));
    - }
    + if (vtime_delta(tsk))
    + account_user_time(tsk, get_vtime_delta(tsk));
    write_seqcount_end(&tsk->vtime_seqcount);
    }

    @@ -776,9 +769,7 @@ EXPORT_SYMBOL_GPL(vtime_guest_exit);

    void vtime_account_idle(struct task_struct *tsk)
    {
    - cputime_t delta_cpu = get_vtime_delta(tsk);
    -
    - account_idle_time(cputime_to_nsecs(delta_cpu));
    + account_idle_time(get_vtime_delta(tsk));
    }

    void arch_vtime_task_switch(struct task_struct *prev)
    @@ -818,7 +809,7 @@ u64 task_gtime(struct task_struct *t)

    gtime = t->gtime;
    if (t->vtime_snap_whence == VTIME_SYS && t->flags & PF_VCPU)
    - gtime += cputime_to_nsecs(vtime_delta(t));
    + gtime += vtime_delta(t);

    } while (read_seqcount_retry(&t->vtime_seqcount, seq));

    @@ -851,7 +842,7 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
    if (t->vtime_snap_whence == VTIME_INACTIVE || is_idle_task(t))
    continue;

    - delta = cputime_to_nsecs(vtime_delta(t));
    + delta = vtime_delta(t);

    /*
    * Task runs either in user or kernel space, add pending nohz time to
    --
    2.7.4
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