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hrtimer: make select() and poll() use the hrtimer range feature

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This patch makes the select() and poll() hrtimers use the new range
feature and settings from the task struct.

In addition, this includes the estimate_accuracy() function that Linus
posted to lkml, but changed entirely based on other peoples lkml feedback.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
This commit is contained in:
Arjan van de Ven 2008-09-01 15:55:35 -07:00
parent 6976675d94
commit 90d6e24a36
1 changed files with 62 additions and 2 deletions
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64
fs/select.c
View file

@ -28,6 +28,58 @@
#include <asm/uaccess.h>
/*
* Estimate expected accuracy in ns from a timeval.
*
* After quite a bit of churning around, we've settled on
* a simple thing of taking 0.1% of the timeout as the
* slack, with a cap of 100 msec.
* "nice" tasks get a 0.5% slack instead.
*
* Consider this comment an open invitation to come up with even
* better solutions..
*/
static unsigned long __estimate_accuracy(struct timespec *tv)
{
unsigned long slack;
int divfactor = 1000;
if (task_nice(current))
divfactor = divfactor / 5;
slack = tv->tv_nsec / divfactor;
slack += tv->tv_sec * (NSEC_PER_SEC/divfactor);
if (slack > 100 * NSEC_PER_MSEC)
slack = 100 * NSEC_PER_MSEC;
return slack;
}
static unsigned long estimate_accuracy(struct timespec *tv)
{
unsigned long ret;
struct timespec now;
/*
* Realtime tasks get a slack of 0 for obvious reasons.
*/
if (current->policy == SCHED_FIFO ||
current->policy == SCHED_RR)
return 0;
ktime_get_ts(&now);
now = timespec_sub(*tv, now);
ret = __estimate_accuracy(&now);
if (ret < current->timer_slack_ns)
return current->timer_slack_ns;
return ret;
}
struct poll_table_page {
struct poll_table_page * next;
struct poll_table_entry * entry;
@ -262,6 +314,7 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
struct poll_wqueues table;
poll_table *wait;
int retval, i, timed_out = 0;
unsigned long slack = 0;
rcu_read_lock();
retval = max_select_fd(n, fds);
@ -278,6 +331,9 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
timed_out = 1;
}
if (end_time)
slack = estimate_accuracy(end_time);
retval = 0;
for (;;) {
unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
@ -353,7 +409,7 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
to = &expire;
}
if (!schedule_hrtimeout(to, HRTIMER_MODE_ABS))
if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
timed_out = 1;
}
__set_current_state(TASK_RUNNING);
@ -593,6 +649,7 @@ static int do_poll(unsigned int nfds, struct poll_list *list,
poll_table* pt = &wait->pt;
ktime_t expire, *to = NULL;
int timed_out = 0, count = 0;
unsigned long slack = 0;
/* Optimise the no-wait case */
if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
@ -600,6 +657,9 @@ static int do_poll(unsigned int nfds, struct poll_list *list,
timed_out = 1;
}
if (end_time)
slack = estimate_accuracy(end_time);
for (;;) {
struct poll_list *walk;
@ -646,7 +706,7 @@ static int do_poll(unsigned int nfds, struct poll_list *list,
to = &expire;
}
if (!schedule_hrtimeout(to, HRTIMER_MODE_ABS))
if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
timed_out = 1;
}
__set_current_state(TASK_RUNNING);