On Mon, 25 Jun 2007 23:09:46 +0200
Roman Zippel <[email protected]> wrote:
> Hi,
>
> On Monday 25 June 2007, Ingo Molnar wrote:
>
> > the patch improves the sysbench OLTP macrobenchmark significantly:
>
> Has that any real practical relevance?
Interesting question. The patch adds a new test-n-branch to gettimeofday()
so if gettimeofday() is used much more frequently than time(), we lose.
> > @@ -373,6 +376,20 @@ void do_gettimeofday (struct timeval *tv
> >
> > tv->tv_sec = sec;
> > tv->tv_usec = usec;
> > +
> > + /*
> > + * Make sure xtime.tv_sec [returned by sys_time()] always
> > + * follows the gettimeofday() result precisely. This
> > + * condition is extremely unlikely, it can hit at most
> > + * once per second:
> > + */
> > + if (unlikely(xtime.tv_sec != tv->tv_sec)) {
> > + unsigned long flags;
> > +
> > + write_seqlock_irqsave(&xtime_lock);
> > + update_wall_time();
> > + write_seqlock_irqrestore(&xtime_lock);
> > + }
> > }
> >
> > EXPORT_SYMBOL(do_gettimeofday);
>
> Is this the do_gettimeofday() inside CONFIG_TIME_INTERPOLATION?
Yes.
> What did you test?
> There can be many ways to read the clock, do you want to put this hook
> everywhere?
Yeah, it isn't immediately obvious (to this little black duck) why similar
fixups weren't needed in timekeeping.c.
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