Messages in this thread | | | Subject | Re: [PATCH 5/6] Export ns irqtimes through /proc/stat -v1 | From | Peter Zijlstra <> | Date | Tue, 26 Oct 2010 16:57:26 +0200 |
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On Tue, 2010-10-26 at 11:45 +0200, Peter Zijlstra wrote: > On Mon, 2010-10-25 at 15:30 -0700, Venkatesh Pallipadi wrote: > > +static void irqtime_account_process_tick(struct task_struct *p, int user_tick, > > + struct rq *rq) > > +{ > > + cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy); > > + cputime64_t tmp = cputime_to_cputime64(cputime_one_jiffy); > > + struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat; > > + > > + if (irqtime_account_hi_update()) { > > + cpustat->irq = cputime64_add(cpustat->irq, tmp); > > + } else if (irqtime_account_si_update()) { > > + cpustat->softirq = cputime64_add(cpustat->softirq, tmp); > > + } else > > I'm still not sure about this else stmt, the above two conditions can > basically 'eat' user/system ticks. What we need to show is that there is > no bias towards either kind so the ratio is not affected -- can we make > such an argument?
I think I can made a counter-argument: if either or both of these checks are true we had system time in the last tick, hence there is a larger chance this tick is a system tick.
Therefore it will not provide the same user/system ratio.
Hmm?
> > if (user_tick) { > > + account_user_time(p, cputime_one_jiffy, one_jiffy_scaled); > > + } else if (p == rq->idle) { > > + account_idle_time(cputime_one_jiffy); > > + } else if (p->flags & PF_VCPU) { /* System time or guest time */ > > + account_guest_time(p, cputime_one_jiffy, one_jiffy_scaled); > > + } else { > > + __account_system_time(p, cputime_one_jiffy, one_jiffy_scaled, > > + &cpustat->system); > > + } > > +}
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