git: 6fa041d7f125 - main - Measure latency of PMC interruptions
Wojciech Macek
wma at FreeBSD.org
Mon Sep 13 04:11:30 UTC 2021
The branch main has been updated by wma:
URL: https://cgit.FreeBSD.org/src/commit/?id=6fa041d7f125db65f400af7f520a41ff78d19cd7
commit 6fa041d7f125db65f400af7f520a41ff78d19cd7
Author: Wojciech Macek <wma at FreeBSD.org>
AuthorDate: 2021-09-13 04:08:32 +0000
Commit: Wojciech Macek <wma at FreeBSD.org>
CommitDate: 2021-09-13 04:08:32 +0000
Measure latency of PMC interruptions
Add HWPMC events to measure latency.
Provide sysctl to choose the number of outstanding events which
trigger HWPMC event.
Obtained from: Semihalf
Sponsored by: Stormshield
Differential revision: https://reviews.freebsd.org/D31283
---
sys/kern/kern_intr.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 52 insertions(+), 6 deletions(-)
diff --git a/sys/kern/kern_intr.c b/sys/kern/kern_intr.c
index 1660414a50ef..19401877dfbd 100644
--- a/sys/kern/kern_intr.c
+++ b/sys/kern/kern_intr.c
@@ -30,6 +30,7 @@
__FBSDID("$FreeBSD$");
#include "opt_ddb.h"
+#include "opt_hwpmc_hooks.h"
#include "opt_kstack_usage_prof.h"
#include <sys/param.h>
@@ -75,6 +76,7 @@ struct intr_thread {
struct thread *it_thread; /* Kernel thread. */
int it_flags; /* (j) IT_* flags. */
int it_need; /* Needs service. */
+ int it_waiting; /* Waiting in the runq. */
};
/* Interrupt thread flags kept in it_flags */
@@ -100,13 +102,19 @@ SYSCTL_INT(_hw, OID_AUTO, intr_storm_threshold, CTLFLAG_RWTUN,
static int intr_epoch_batch = 1000;
SYSCTL_INT(_hw, OID_AUTO, intr_epoch_batch, CTLFLAG_RWTUN, &intr_epoch_batch,
0, "Maximum interrupt handler executions without re-entering epoch(9)");
+#ifdef HWPMC_HOOKS
+static int intr_hwpmc_waiting_report_threshold = 1;
+SYSCTL_INT(_hw, OID_AUTO, intr_hwpmc_waiting_report_threshold, CTLFLAG_RWTUN,
+ &intr_hwpmc_waiting_report_threshold, 1,
+ "Threshold for reporting number of events in a workq");
+#endif
static TAILQ_HEAD(, intr_event) event_list =
TAILQ_HEAD_INITIALIZER(event_list);
static struct mtx event_lock;
MTX_SYSINIT(intr_event_list, &event_lock, "intr event list", MTX_DEF);
static void intr_event_update(struct intr_event *ie);
-static int intr_event_schedule_thread(struct intr_event *ie);
+static int intr_event_schedule_thread(struct intr_event *ie, struct trapframe *frame);
static struct intr_thread *ithread_create(const char *name);
static void ithread_destroy(struct intr_thread *ithread);
static void ithread_execute_handlers(struct proc *p,
@@ -115,6 +123,16 @@ static void ithread_loop(void *);
static void ithread_update(struct intr_thread *ithd);
static void start_softintr(void *);
+#ifdef HWPMC_HOOKS
+#include <sys/pmckern.h>
+PMC_SOFT_DEFINE( , , intr, all);
+PMC_SOFT_DEFINE( , , intr, ithread);
+PMC_SOFT_DEFINE( , , intr, filter);
+PMC_SOFT_DEFINE( , , intr, stray);
+PMC_SOFT_DEFINE( , , intr, schedule);
+PMC_SOFT_DEFINE( , , intr, waiting);
+#endif
+
/* Map an interrupt type to an ithread priority. */
u_char
intr_priority(enum intr_type flags)
@@ -773,7 +791,7 @@ intr_handler_barrier(struct intr_handler *handler)
}
if ((handler->ih_flags & IH_CHANGED) == 0) {
handler->ih_flags |= IH_CHANGED;
- intr_event_schedule_thread(ie);
+ intr_event_schedule_thread(ie, NULL);
}
while ((handler->ih_flags & IH_CHANGED) != 0)
msleep(handler, &ie->ie_lock, 0, "ih_barr", 0);
@@ -872,7 +890,7 @@ intr_event_remove_handler(void *cookie)
KASSERT((handler->ih_flags & IH_DEAD) == 0,
("duplicate handle remove"));
handler->ih_flags |= IH_DEAD;
- intr_event_schedule_thread(ie);
+ intr_event_schedule_thread(ie, NULL);
while (handler->ih_flags & IH_DEAD)
msleep(handler, &ie->ie_lock, 0, "iev_rmh", 0);
intr_event_update(ie);
@@ -944,7 +962,7 @@ intr_event_resume_handler(void *cookie)
}
static int
-intr_event_schedule_thread(struct intr_event *ie)
+intr_event_schedule_thread(struct intr_event *ie, struct trapframe *frame)
{
struct intr_entropy entropy;
struct intr_thread *it;
@@ -986,11 +1004,28 @@ intr_event_schedule_thread(struct intr_event *ie)
atomic_store_rel_int(&it->it_need, 1);
thread_lock(td);
if (TD_AWAITING_INTR(td)) {
+#ifdef HWPMC_HOOKS
+ atomic_set_int(&it->it_waiting, 0);
+ if (frame != NULL)
+ PMC_SOFT_CALL_TF( , , intr, schedule, frame);
+ else
+ PMC_SOFT_CALL( , , intr, schedule);
+#endif
CTR3(KTR_INTR, "%s: schedule pid %d (%s)", __func__, td->td_proc->p_pid,
td->td_name);
TD_CLR_IWAIT(td);
sched_add(td, SRQ_INTR);
} else {
+#ifdef HWPMC_HOOKS
+ atomic_add_int(&it->it_waiting, 1);
+
+ if (atomic_load_int(&it->it_waiting) >= intr_hwpmc_waiting_report_threshold) {
+ if (frame != NULL)
+ PMC_SOFT_CALL_TF( , , intr, waiting, frame);
+ else
+ PMC_SOFT_CALL( , , intr, waiting);
+ }
+#endif
CTR5(KTR_INTR, "%s: pid %d (%s): it_need %d, state %d",
__func__, td->td_proc->p_pid, td->td_name, it->it_need, TD_GET_STATE(td));
thread_unlock(td);
@@ -1083,7 +1118,7 @@ swi_sched(void *cookie, int flags)
#endif
} else {
VM_CNT_INC(v_soft);
- error = intr_event_schedule_thread(ie);
+ error = intr_event_schedule_thread(ie, NULL);
KASSERT(error == 0, ("stray software interrupt"));
}
}
@@ -1374,12 +1409,23 @@ intr_event_handle(struct intr_event *ie, struct trapframe *frame)
ret = ih->ih_filter(frame);
else
ret = ih->ih_filter(ih->ih_argument);
+#ifdef HWPMC_HOOKS
+ PMC_SOFT_CALL_TF( , , intr, all, frame);
+#endif
KASSERT(ret == FILTER_STRAY ||
((ret & (FILTER_SCHEDULE_THREAD | FILTER_HANDLED)) != 0 &&
(ret & ~(FILTER_SCHEDULE_THREAD | FILTER_HANDLED)) == 0),
("%s: incorrect return value %#x from %s", __func__, ret,
ih->ih_name));
filter = filter || ret == FILTER_HANDLED;
+#ifdef HWPMC_HOOKS
+ if (ret & FILTER_SCHEDULE_THREAD)
+ PMC_SOFT_CALL_TF( , , intr, ithread, frame);
+ else if (ret & FILTER_HANDLED)
+ PMC_SOFT_CALL_TF( , , intr, filter, frame);
+ else if (ret == FILTER_STRAY)
+ PMC_SOFT_CALL_TF( , , intr, stray, frame);
+#endif
/*
* Wrapper handler special handling:
@@ -1416,7 +1462,7 @@ intr_event_handle(struct intr_event *ie, struct trapframe *frame)
if (thread) {
int error __unused;
- error = intr_event_schedule_thread(ie);
+ error = intr_event_schedule_thread(ie, frame);
KASSERT(error == 0, ("bad stray interrupt"));
}
critical_exit();
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