On 08/21, Peter Zijlstra wrote:
>
> On Wed, Aug 21, 2013 at 01:35:51PM +0200, Oleg Nesterov wrote:
> >
> > Well, the only overhead is "if(to == MAX_SCHEDULE_TIMEOUT)" at the start.
> > I don't think it makes sense to copy-and-paste the identical code to
> > avoid it. But please ignore, this is really minor and off-topic.
>
> Ah, so the 'problem' is that schedule_timeout() doesn't live in
> kernel/sched/core.c and we thus get an extra function call (which are
> somewhat expensive on some archs).
So, unlike me, you like -02 more than -Os ;)
> +static inline long schedule_timeout(long timeout)
> +{
> + if (timeout == MAX_SCHEDULE_TIMEOUT) {
> + schedule();
> + return timeout;
> + }
> + return __schedule_timeout(timeout);
> +}
Well this means that every caller will do the MAX_SCHEDULE_TIMEOUT
check inline, and this case is unlikely. And you are also going
to make schedule_timeout_*() inline...
But,
> +static inline long schedule_timeout_interruptible(long timeout)
> +{
> + __set_current_state(TASK_INTERRUPTIBLE);
> + return schedule_timeout(timeout);
> +}
> +static inline long schedule_timeout_killable(long timeout)
> +{
> + __set_current_state(TASK_KILLABLE);
> + return schedule_timeout(timeout);
> +}
> +static inline long schedule_timeout_uninterruptible(long timeout)
> +{
> + __set_current_state(TASK_UNINTERRUPTIBLE);
> + return schedule_timeout(timeout);
> +}
> ...
> -signed long __sched schedule_timeout_interruptible(signed long timeout)
> -{
> - __set_current_state(TASK_INTERRUPTIBLE);
> - return schedule_timeout(timeout);
> -}
> -EXPORT_SYMBOL(schedule_timeout_interruptible);
> -
> -signed long __sched schedule_timeout_killable(signed long timeout)
> -{
> - __set_current_state(TASK_KILLABLE);
> - return schedule_timeout(timeout);
> -}
> -EXPORT_SYMBOL(schedule_timeout_killable);
> -
> -signed long __sched schedule_timeout_uninterruptible(signed long timeout)
> -{
> - __set_current_state(TASK_UNINTERRUPTIBLE);
> - return schedule_timeout(timeout);
> -}
> -EXPORT_SYMBOL(schedule_timeout_uninterruptible);
> +EXPORT_SYMBOL(__schedule_timeout);
personally I think this particular change is fine.
Or we can export a single schedule_timeout_state(timeout, state) to
factor out get_current().
But just in case, of course I won't argue in any case.
Oleg.
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