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Detect interrupt storms better. The storm detection didn't work at all

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with an ASUS A7N8X-E motherboard in APIC mode, since storming interrupts
don't repeat immediately.  Use DELAY(1) to wait a bit for them to repeat.
This affects all systems.  Only delay for the first
(10 * intr_storm_threshold) interrupts (per interrupt handler) so that
this is only a pessimization while warming up.  Throttle after calling
the sub-handlers instead of before so that the long delay given by
throttling can be used instead of the DELAY(1) to detect storms after
warming up.

Reduced the throttling period from 1/10 second to 1/hz seconds so that
throttling doesn't destroy performance so much.  Interrupts that are
detected as storming are effectively handled by polling at a frequency
of hz Hz.  On A7N8X-E's there is another hardware or configuration bug
that makes the throttled frequency closer to 2*hz Hz.
This commit is contained in:
Bruce Evans 2004-06-05 18:27:28 +00:00
parent b612d5e1ea
commit 05b2c96fd3
1 changed files with 50 additions and 23 deletions
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73
sys/kern/kern_intr.c
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@ -38,6 +38,7 @@ __FBSDID("$FreeBSD$");
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/ktr.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
@ -494,14 +495,14 @@ ithread_loop(void *arg)
struct intrhand *ih; /* and our interrupt handler chain */
struct thread *td;
struct proc *p;
int count, warned;
int count, warming, warned;
td = curthread;
p = td->td_proc;
ithd = (struct ithd *)arg; /* point to myself */
KASSERT(ithd->it_td == td && td->td_ithd == ithd,
("%s: ithread and proc linkage out of sync", __func__));
count = 0;
warming = 10 * intr_storm_threshold;
warned = 0;
/*
@ -523,6 +524,7 @@ ithread_loop(void *arg)
CTR4(KTR_INTR, "%s: pid %d: (%s) need=%d", __func__,
p->p_pid, p->p_comm, ithd->it_need);
count = 0;
while (ithd->it_need) {
/*
* Service interrupts. If another interrupt
@ -531,25 +533,6 @@ ithread_loop(void *arg)
* another pass.
*/
atomic_store_rel_int(&ithd->it_need, 0);
/*
* If we detect an interrupt storm, pause with
* the source masked for 1/10th of a second.
*/
if (intr_storm_threshold != 0 && count >=
intr_storm_threshold) {
if (!warned) {
printf(
"Interrupt storm detected on \"%s\"; throttling interrupt source\n",
p->p_comm);
warned = 1;
}
tsleep(&count, td->td_priority, "istorm",
hz / 10);
count = 0;
} else
count++;
restart:
TAILQ_FOREACH(ih, &ithd->it_handlers, ih_next) {
if (ithd->it_flags & IT_SOFT && !ih->ih_need)
@ -575,8 +558,53 @@ ithread_loop(void *arg)
if ((ih->ih_flags & IH_MPSAFE) == 0)
mtx_unlock(&Giant);
}
if (ithd->it_enable != NULL)
if (ithd->it_enable != NULL) {
ithd->it_enable(ithd->it_vector);
/*
* Storm detection needs a delay here
* to see slightly delayed interrupts
* on some machines, but we don't
* want to always delay, so only delay
* while warming up.
*/
if (warming != 0) {
DELAY(1);
--warming;
}
}
/*
* If we detect an interrupt storm, sleep until
* the next hardclock tick. We sleep at the
* end of the loop instead of at the beginning
* to ensure that we see slightly delayed
* interrupts.
*/
if (count >= intr_storm_threshold) {
if (!warned) {
printf(
"Interrupt storm detected on \"%s\"; throttling interrupt source\n",
p->p_comm);
warned = 1;
}
tsleep(&count, td->td_priority, "istorm", 1);
/*
* Fudge the count to re-throttle if the
* interrupt is still active. Our storm
* detection is too primitive to detect
* whether the storm has gone away
* reliably, even if we were to waste a
* lot of time spinning for the next
* intr_storm_threshold interrupts, so
* we assume that the storm hasn't gone
* away unless the interrupt repeats
* less often the hardclock interrupt.
*/
count = INT_MAX - 1;
}
count++;
}
WITNESS_WARN(WARN_PANIC, NULL, "suspending ithread");
mtx_assert(&Giant, MA_NOTOWNED);
@ -589,7 +617,6 @@ ithread_loop(void *arg)
mtx_lock_spin(&sched_lock);
if (!ithd->it_need) {
TD_SET_IWAIT(td);
count = 0;
CTR2(KTR_INTR, "%s: pid %d: done", __func__, p->p_pid);
mi_switch(SW_VOL);
CTR2(KTR_INTR, "%s: pid %d: resumed", __func__, p->p_pid);