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    SubjectRe: [PATCH 5/7] KVM-GST: KVM Steal time accounting
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    On Mon, 2011-06-13 at 19:31 -0400, Glauber Costa wrote:
    > +static inline int touch_steal_time(int is_idle)
    > +{
    > + u64 steal, st = 0;
    > +
    > + if (static_branch(&paravirt_steal_enabled)) {
    > +
    > + steal = paravirt_steal_clock(smp_processor_id());
    > +
    > + steal -= this_rq()->prev_steal_time;
    > + this_rq()->prev_steal_time += steal;

    If you move this addition below this test:

    > + if (is_idle || (steal < TICK_NSEC))
    > + return 0;

    that is, right here, then you don't loose tiny steal deltas and
    subsequent ticks accumulate their steal time until you really
    have a full steal tick to account.

    I guess you want something different for the idle case though.

    > + while (steal > TICK_NSEC) {

    /* really, if we wanted a division we'd have written one */
    asm("" : "+rm" (steal));

    > + steal -= TICK_NSEC;
    > + st++;
    > + }
    > +
    > + account_steal_time(st);
    > + return 1;
    > + }
    > + return 0;
    > +}




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