The branch stable/13 has been updated by mav:
URL:
https://cgit.FreeBSD.org/src/commit/?id=4a58aca40df9a5a5e5db430f3744a2712f955ed7
commit 4a58aca40df9a5a5e5db430f3744a2712f955ed7
Author: Alexander Motin <m...@freebsd.org>
AuthorDate: 2021-06-25 17:52:58 +0000
Commit: Alexander Motin <m...@freebsd.org>
CommitDate: 2021-07-09 01:38:32 +0000
Allow sleepq_signal() to drop the lock.
Introduce SLEEPQ_DROP sleepq_signal() flag, allowing one to drop the
sleep queue chain lock before returning. Reduced lock scope allows
significantly reduce lock contention inside taskqueue_enqueue() for
ZFS worker threads doing ~350K disk reads/s on 40-thread system.
MFC after: 2 weeks
Sponsored by: iXsystems, Inc.
(cherry picked from commit 6df35af4d85c6311d8e762521580e7176b69394e)
---
sys/kern/kern_synch.c | 8 +++-----
sys/kern/subr_sleepqueue.c | 8 ++++++--
sys/sys/sleepqueue.h | 1 +
3 files changed, 10 insertions(+), 7 deletions(-)
diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c
index 4c0491ab6e85..b63877e26b68 100644
--- a/sys/kern/kern_synch.c
+++ b/sys/kern/kern_synch.c
@@ -366,8 +366,7 @@ wakeup_one(const void *ident)
int wakeup_swapper;
sleepq_lock(ident);
- wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP, 0, 0);
- sleepq_release(ident);
+ wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP | SLEEPQ_DROP, 0, 0);
if (wakeup_swapper)
kick_proc0();
}
@@ -378,9 +377,8 @@ wakeup_any(const void *ident)
int wakeup_swapper;
sleepq_lock(ident);
- wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP | SLEEPQ_UNFAIR,
- 0, 0);
- sleepq_release(ident);
+ wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP | SLEEPQ_UNFAIR |
+ SLEEPQ_DROP, 0, 0);
if (wakeup_swapper)
kick_proc0();
}
diff --git a/sys/kern/subr_sleepqueue.c b/sys/kern/subr_sleepqueue.c
index 0718f01fa48a..b146a978a60c 100644
--- a/sys/kern/subr_sleepqueue.c
+++ b/sys/kern/subr_sleepqueue.c
@@ -927,8 +927,11 @@ sleepq_signal(const void *wchan, int flags, int pri, int
queue)
KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
MPASS((queue >= 0) && (queue < NR_SLEEPQS));
sq = sleepq_lookup(wchan);
- if (sq == NULL)
+ if (sq == NULL) {
+ if (flags & SLEEPQ_DROP)
+ sleepq_release(wchan);
return (0);
+ }
KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
("%s: mismatch between sleep/wakeup and cv_*", __func__));
@@ -961,7 +964,8 @@ sleepq_signal(const void *wchan, int flags, int pri, int
queue)
}
}
MPASS(besttd != NULL);
- wakeup_swapper = sleepq_resume_thread(sq, besttd, pri, SRQ_HOLD);
+ wakeup_swapper = sleepq_resume_thread(sq, besttd, pri,
+ (flags & SLEEPQ_DROP) ? 0 : SRQ_HOLD);
return (wakeup_swapper);
}
diff --git a/sys/sys/sleepqueue.h b/sys/sys/sleepqueue.h
index 18c7568777b6..6715894ed1f3 100644
--- a/sys/sys/sleepqueue.h
+++ b/sys/sys/sleepqueue.h
@@ -85,6 +85,7 @@ struct thread;
#define SLEEPQ_LK 0x04 /* Used by a lockmgr. */
#define SLEEPQ_INTERRUPTIBLE 0x100 /* Sleep is
interruptible. */
#define SLEEPQ_UNFAIR 0x200 /* Unfair wakeup order.
*/
+#define SLEEPQ_DROP 0x400 /* Return without lock
held. */
void init_sleepqueues(void);
int sleepq_abort(struct thread *td, int intrval);
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