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..
---
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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