The branch main has been updated by wma:
URL:
https://cgit.FreeBSD.org/src/commit/?id=7bc13692a2d6b33b4e80bb9ad70d5eede6b148af
commit 7bc13692a2d6b33b4e80bb9ad70d5eede6b148af
Author: Wojciech Macek <w...@freebsd.org>
AuthorDate: 2021-09-20 11:08:32 +0000
Commit: Wojciech Macek <w...@freebsd.org>
CommitDate: 2021-09-23 05:15:42 +0000
hwpmc: fix performance issues
Differential revision: https://reviews.freebsd.org/D32025
Avoid using atomics as it_wait is guarded by td_lock.
Report threshold calculation is done only if at least one PMC hook
is installed
Fixes:
* avoid unnecessary branching (if frame != null ...)
by having PMC_HOOK_INSTALLED_ANY
condition on the top of them, which should hint
the core not to execute speculatively anything
which us underneath;
* access intr_hwpmc_waiting_report_threshold cacheline
only if at least one hook is loaded;
---
sys/kern/kern_intr.c | 29 ++++++++++++++++-------------
1 file changed, 16 insertions(+), 13 deletions(-)
diff --git a/sys/kern/kern_intr.c b/sys/kern/kern_intr.c
index 19401877dfbd..4e6e575a9fc9 100644
--- a/sys/kern/kern_intr.c
+++ b/sys/kern/kern_intr.c
@@ -107,6 +107,7 @@ 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");
+#define PMC_HOOK_INSTALLED_ANY() __predict_false(pmc_hook != NULL)
#endif
static TAILQ_HEAD(, intr_event) event_list =
TAILQ_HEAD_INITIALIZER(event_list);
@@ -131,6 +132,14 @@ PMC_SOFT_DEFINE( , , intr, filter);
PMC_SOFT_DEFINE( , , intr, stray);
PMC_SOFT_DEFINE( , , intr, schedule);
PMC_SOFT_DEFINE( , , intr, waiting);
+
+#define PMC_SOFT_CALL_INTR_HLPR(event, frame) \
+do { \
+ if (frame != NULL) \
+ PMC_SOFT_CALL_TF( , , intr, event, frame); \
+ else \
+ PMC_SOFT_CALL( , , intr, event); \
+} while (0)
#endif
/* Map an interrupt type to an ithread priority. */
@@ -1005,11 +1014,9 @@ intr_event_schedule_thread(struct intr_event *ie, struct
trapframe *frame)
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);
+ it->it_waiting = 0;
+ if (PMC_HOOK_INSTALLED_ANY())
+ PMC_SOFT_CALL_INTR_HLPR(schedule, frame);
#endif
CTR3(KTR_INTR, "%s: schedule pid %d (%s)", __func__,
td->td_proc->p_pid,
td->td_name);
@@ -1017,14 +1024,10 @@ intr_event_schedule_thread(struct intr_event *ie,
struct trapframe *frame)
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);
- }
+ it->it_waiting++;
+ if (PMC_HOOK_INSTALLED_ANY() &&
+ (it->it_waiting >= intr_hwpmc_waiting_report_threshold))
+ PMC_SOFT_CALL_INTR_HLPR(waiting, frame);
#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));
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