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SGI Altix IA64 mmtimer: eliminate long interval timer holdoffs

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This patch for SGI Altix/IA64 eliminates interval long timer holdoffs in
cases where we don't start an interval timer before the expiration time.
This sometimes happens when a number of interval timers on the same shub
with the same interval run simultaneously.

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Dimitri Sivanich 2010-10-27 15:34:20 -07:00 • committed by Linus Torvalds
parent 656e17ea9d
commit dcade5ed16
1 changed files with 32 additions and 28 deletions
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60
drivers/char/mmtimer.c
View file

@ -176,9 +176,9 @@ static void mmtimer_setup_int_2(int cpu, u64 expires)
* in order to insure that the setup succeeds in a deterministic time frame.
* It will check if the interrupt setup succeeded.
*/
static int mmtimer_setup(int cpu, int comparator, unsigned long expires)
static int mmtimer_setup(int cpu, int comparator, unsigned long expires,
u64 *set_completion_time)
{
switch (comparator) {
case 0:
mmtimer_setup_int_0(cpu, expires);
@ -191,7 +191,8 @@ static int mmtimer_setup(int cpu, int comparator, unsigned long expires)
break;
}
/* We might've missed our expiration time */
if (rtc_time() <= expires)
*set_completion_time = rtc_time();
if (*set_completion_time <= expires)
return 1;
/*
@ -227,6 +228,8 @@ static int mmtimer_disable_int(long nasid, int comparator)
#define TIMER_OFF 0xbadcabLL /* Timer is not setup */
#define TIMER_SET 0 /* Comparator is set for this timer */
#define MMTIMER_INTERVAL_RETRY_INCREMENT_DEFAULT 40
/* There is one of these for each timer */
struct mmtimer {
struct rb_node list;
@ -242,6 +245,11 @@ struct mmtimer_node {
};
static struct mmtimer_node *timers;
static unsigned mmtimer_interval_retry_increment =
MMTIMER_INTERVAL_RETRY_INCREMENT_DEFAULT;
module_param(mmtimer_interval_retry_increment, uint, 0644);
MODULE_PARM_DESC(mmtimer_interval_retry_increment,
"RTC ticks to add to expiration on interval retry (default 40)");
/*
* Add a new mmtimer struct to the node's mmtimer list.
@ -289,7 +297,8 @@ static void mmtimer_set_next_timer(int nodeid)
struct mmtimer_node *n = &timers[nodeid];
struct mmtimer *x;
struct k_itimer *t;
int o;
u64 expires, exp, set_completion_time;
int i;
restart:
if (n->next == NULL)
@ -300,7 +309,8 @@ static void mmtimer_set_next_timer(int nodeid)
if (!t->it.mmtimer.incr) {
/* Not an interval timer */
if (!mmtimer_setup(x->cpu, COMPARATOR,
t->it.mmtimer.expires)) {
t->it.mmtimer.expires,
&set_completion_time)) {
/* Late setup, fire now */
tasklet_schedule(&n->tasklet);
}
@ -308,14 +318,23 @@ static void mmtimer_set_next_timer(int nodeid)
}
/* Interval timer */
o = 0;
while (!mmtimer_setup(x->cpu, COMPARATOR, t->it.mmtimer.expires)) {
unsigned long e, e1;
struct rb_node *next;
t->it.mmtimer.expires += t->it.mmtimer.incr << o;
t->it_overrun += 1 << o;
o++;
if (o > 20) {
i = 0;
expires = exp = t->it.mmtimer.expires;
while (!mmtimer_setup(x->cpu, COMPARATOR, expires,
&set_completion_time)) {
int to;
i++;
expires = set_completion_time +
mmtimer_interval_retry_increment + (1 << i);
/* Calculate overruns as we go. */
to = ((u64)(expires - exp) / t->it.mmtimer.incr);
if (to) {
t->it_overrun += to;
t->it.mmtimer.expires += t->it.mmtimer.incr * to;
exp = t->it.mmtimer.expires;
}
if (i > 20) {
printk(KERN_ALERT "mmtimer: cannot reschedule timer\n");
t->it.mmtimer.clock = TIMER_OFF;
n->next = rb_next(&x->list);
@ -323,21 +342,6 @@ static void mmtimer_set_next_timer(int nodeid)
kfree(x);
goto restart;
}
e = t->it.mmtimer.expires;
next = rb_next(&x->list);
if (next == NULL)
continue;
e1 = rb_entry(next, struct mmtimer, list)->
timer->it.mmtimer.expires;
if (e > e1) {
n->next = next;
rb_erase(&x->list, &n->timer_head);
mmtimer_add_list(x);
goto restart;
}
}
}