On Thu, Nov 18, 2010 at 09:04:34PM +0800, Peter Zijlstra wrote:
> On Wed, 2010-11-17 at 12:27 +0800, Wu Fengguang wrote:
> > - avoid useless (eg. zero pause time) balance_dirty_pages() calls
> > - avoid too small pause time (less than 10ms, which burns CPU power)
> > - avoid too large pause time (more than 100ms, which hurts responsiveness)
> > - avoid big fluctuations of pause times
>
> If you feel like playing with sub-jiffies timeouts (a way to avoid that
> HZ=>100 assumption), the below (totally untested) patch might be of
> help..
Assuming there are HZ=10 users.
- when choosing such a coarse granularity, do they really care about
responsiveness? :)
- will the use of hrtimer add a little code size and/or runtime
overheads, and hence hurt the majority HZ=100 users?
Thanks,
Fengguang
>
> ---
> Subject: hrtimer: Provide io_schedule_timeout*() functions
>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> ---
> include/linux/hrtimer.h | 7 +++++++
> kernel/hrtimer.c | 15 +++++++++++++++
> kernel/sched.c | 17 +++++++++++++++++
> 3 files changed, 39 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
> index dd9954b..9e0f67e 100644
> --- a/include/linux/hrtimer.h
> +++ b/include/linux/hrtimer.h
> @@ -419,6 +419,13 @@ extern long hrtimer_nanosleep_restart(struct restart_block *restart_block);
> extern void hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
> struct task_struct *tsk);
>
> +extern int io_schedule_hrtimeout_range(ktime_t *expires, unsigned long delta,
> + const enum hrtimer_mode mode);
> +extern int io_schedule_hrtimeout_range_clock(ktime_t *expires,
> + unsigned long delta, const enum hrtimer_mode mode, int clock);
> +extern int io_schedule_hrtimeout(ktime_t *expires, const enum hrtimer_mode mode);
> +
> +
> extern int schedule_hrtimeout_range(ktime_t *expires, unsigned long delta,
> const enum hrtimer_mode mode);
> extern int schedule_hrtimeout_range_clock(ktime_t *expires,
> diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
> index 72206cf..ef2d93c 100644
> --- a/kernel/hrtimer.c
> +++ b/kernel/hrtimer.c
> @@ -1838,6 +1838,14 @@ int __sched schedule_hrtimeout_range(ktime_t *expires, unsigned long delta,
> }
> EXPORT_SYMBOL_GPL(schedule_hrtimeout_range);
>
> +int __sched io_schedule_hrtimeout_range(ktime_t *expires, unsigned long delta,
> + const enum hrtimer_mode mode)
> +{
> + return io_schedule_hrtimeout_range_clock(expires, delta, mode,
> + CLOCK_MONOTONIC);
> +}
> +EXPORT_SYMBOL_GPL(io_schedule_hrtimeout_range);
> +
> /**
> * schedule_hrtimeout - sleep until timeout
> * @expires: timeout value (ktime_t)
> @@ -1866,3 +1874,10 @@ int __sched schedule_hrtimeout(ktime_t *expires,
> return schedule_hrtimeout_range(expires, 0, mode);
> }
> EXPORT_SYMBOL_GPL(schedule_hrtimeout);
> +
> +int __sched io_schedule_hrtimeout(ktime_t *expires,
> + const enum hrtimer_mode mode)
> +{
> + return io_schedule_hrtimeout_range(expires, 0, mode);
> +}
> +EXPORT_SYMBOL_GPL(io_schedule_hrtimeout);
> diff --git a/kernel/sched.c b/kernel/sched.c
> index d5564a8..ac84455 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -5303,6 +5303,23 @@ long __sched io_schedule_timeout(long timeout)
> return ret;
> }
>
> +int __sched
> +io_schedule_hrtimeout_range_clock(ktime_t *expires, unsigned long delta,
> + const enum hrtimer_mode mode, int clock)
> +{
> + struct rq *rq = raw_rq();
> + long ret;
> +
> + delayacct_blkio_start();
> + atomic_inc(&rq->nr_iowait);
> + current->in_iowait = 1;
> + ret = schedule_hrtimeout_range_clock(expires, delta, mode, clock);
> + current->in_iowait = 0;
> + atomic_dec(&rq->nr_iowait);
> + delayacct_blkio_end();
> + return ret;
> +}
> +
> /**
> * sys_sched_get_priority_max - return maximum RT priority.
> * @policy: scheduling class.
>
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