On Wed, 2016-06-22 at 00:28 +0200, Peter Zijlstra wrote:
> On Tue, Jun 21, 2016 at 06:23:34PM -0400, Rik van Riel wrote:
> >
> > > > + /*
> > > > + * Softirq context may get interrupted by hardirq
> > > > context,
> > > > + * on the same CPU. At softirq entry time the amount
> > > > of
> > > > time
> > > > + * spent in hardirq context is stored. At softirq exit
> > > > time,
> > > > + * the time spent in hardirq context during the
> > > > softirq is
> > > > + * subtracted.
> > > > + */
> > > > + prev_hardirq = __this_cpu_read(prev_hardirq_time);
> > > > + prev_softirq_start =
> > > > __this_cpu_read(softirq_start_time);
> > > > +
> > > > + if (irqtype == HARDIRQ_OFFSET) {
> > > > + delta = sched_clock_cpu(cpu) -
> > > > __this_cpu_read(hardirq_start_time);
> > > > + __this_cpu_add(hardirq_start_time, delta);
> > > > + } else do {
> > > > + u64 now = sched_clock_cpu(cpu);
> > > > + hardirq_time =
> > > > READ_ONCE(per_cpu(cpu_hardirq_time,
> > > > cpu));
> > > Which makes this per_cpu(,cpu) usage somewhat curious. What's
> > > wrong
> > > with
> > > __this_cpu_read() ?
> > Is __this_cpu_read() as fast as per_cpu(,cpu) on all
> > architectures?
> Can't be slower. Don't get the argument though; you've used
> __this_cpu
> stuff all over the place, and here you use a per_cpu() for no reason.
>
Good point. I will use __this_cpu_read here.> > > That whole thing is somewhat hard to read; but its far too late > > > for > > > me > > > to suggest anything more readable :/ > > I only had 2 1/2 hours of sleep last night, so I will not > > try to rewrite it now, but I will see if there is anything > > I can do to make it more readable tomorrow. > > > > If you have any ideas before then, please let me know :) > Heh, step away from the computer ... ;-) No worries, I have booze with me. Everything will be just fine! ;) -- All Rights Reversed.
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