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SGI Altix IA64 mmtimer: eliminate long interval timer holdoffs
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>
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656e17ea9d
commit
dcade5ed16
1 changed files with 32 additions and 28 deletions
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@ -176,9 +176,9 @@ static void mmtimer_setup_int_2(int cpu, u64 expires)
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* in order to insure that the setup succeeds in a deterministic time frame.
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* It will check if the interrupt setup succeeded.
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*/
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static int mmtimer_setup(int cpu, int comparator, unsigned long expires)
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static int mmtimer_setup(int cpu, int comparator, unsigned long expires,
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u64 *set_completion_time)
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{
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switch (comparator) {
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case 0:
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mmtimer_setup_int_0(cpu, expires);
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@ -191,7 +191,8 @@ static int mmtimer_setup(int cpu, int comparator, unsigned long expires)
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break;
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}
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/* We might've missed our expiration time */
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if (rtc_time() <= expires)
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*set_completion_time = rtc_time();
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if (*set_completion_time <= expires)
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return 1;
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/*
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@ -227,6 +228,8 @@ static int mmtimer_disable_int(long nasid, int comparator)
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#define TIMER_OFF 0xbadcabLL /* Timer is not setup */
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#define TIMER_SET 0 /* Comparator is set for this timer */
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#define MMTIMER_INTERVAL_RETRY_INCREMENT_DEFAULT 40
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/* There is one of these for each timer */
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struct mmtimer {
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struct rb_node list;
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@ -242,6 +245,11 @@ struct mmtimer_node {
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};
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static struct mmtimer_node *timers;
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static unsigned mmtimer_interval_retry_increment =
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MMTIMER_INTERVAL_RETRY_INCREMENT_DEFAULT;
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module_param(mmtimer_interval_retry_increment, uint, 0644);
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MODULE_PARM_DESC(mmtimer_interval_retry_increment,
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"RTC ticks to add to expiration on interval retry (default 40)");
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/*
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* Add a new mmtimer struct to the node's mmtimer list.
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@ -289,7 +297,8 @@ static void mmtimer_set_next_timer(int nodeid)
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struct mmtimer_node *n = &timers[nodeid];
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struct mmtimer *x;
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struct k_itimer *t;
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int o;
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u64 expires, exp, set_completion_time;
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int i;
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restart:
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if (n->next == NULL)
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@ -300,7 +309,8 @@ static void mmtimer_set_next_timer(int nodeid)
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if (!t->it.mmtimer.incr) {
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/* Not an interval timer */
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if (!mmtimer_setup(x->cpu, COMPARATOR,
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t->it.mmtimer.expires)) {
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t->it.mmtimer.expires,
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&set_completion_time)) {
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/* Late setup, fire now */
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tasklet_schedule(&n->tasklet);
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}
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@ -308,14 +318,23 @@ static void mmtimer_set_next_timer(int nodeid)
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}
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/* Interval timer */
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o = 0;
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while (!mmtimer_setup(x->cpu, COMPARATOR, t->it.mmtimer.expires)) {
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unsigned long e, e1;
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struct rb_node *next;
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t->it.mmtimer.expires += t->it.mmtimer.incr << o;
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t->it_overrun += 1 << o;
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o++;
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if (o > 20) {
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i = 0;
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expires = exp = t->it.mmtimer.expires;
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while (!mmtimer_setup(x->cpu, COMPARATOR, expires,
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&set_completion_time)) {
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int to;
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i++;
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expires = set_completion_time +
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mmtimer_interval_retry_increment + (1 << i);
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/* Calculate overruns as we go. */
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to = ((u64)(expires - exp) / t->it.mmtimer.incr);
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if (to) {
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t->it_overrun += to;
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t->it.mmtimer.expires += t->it.mmtimer.incr * to;
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exp = t->it.mmtimer.expires;
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}
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if (i > 20) {
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printk(KERN_ALERT "mmtimer: cannot reschedule timer\n");
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t->it.mmtimer.clock = TIMER_OFF;
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n->next = rb_next(&x->list);
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@ -323,21 +342,6 @@ static void mmtimer_set_next_timer(int nodeid)
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kfree(x);
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goto restart;
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}
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e = t->it.mmtimer.expires;
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next = rb_next(&x->list);
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if (next == NULL)
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continue;
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e1 = rb_entry(next, struct mmtimer, list)->
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timer->it.mmtimer.expires;
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if (e > e1) {
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n->next = next;
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rb_erase(&x->list, &n->timer_head);
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mmtimer_add_list(x);
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goto restart;
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}
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}
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}
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