The branch main has been updated by trasz:
URL:
https://cgit.FreeBSD.org/src/commit/?id=e7a5b3bd058975ff3ffa346664690e54c641fc0f
commit e7a5b3bd058975ff3ffa346664690e54c641fc0f
Author: Edward Tomasz Napierala <tr...@freebsd.org>
AuthorDate: 2021-02-25 18:48:50 +0000
Commit: Edward Tomasz Napierala <tr...@freebsd.org>
CommitDate: 2021-02-25 18:55:26 +0000
Modify lock_delay() to increase the delay time after spinning
Modify lock_delay() to increase the delay time after spinning,
not before. Previously we would spin at least twice instead of once.
In NetApp's benchmarks this fixes a performance regression compared
to FreeBSD 10, which called cpu_spinwait() directly.
Reviewed By: mjg
Sponsored by: NetApp, Inc.
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D27331
---
sys/kern/subr_lock.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/sys/kern/subr_lock.c b/sys/kern/subr_lock.c
index a74f7e62db4a..8b08c61715b3 100644
--- a/sys/kern/subr_lock.c
+++ b/sys/kern/subr_lock.c
@@ -128,10 +128,6 @@ lock_delay(struct lock_delay_arg *la)
struct lock_delay_config *lc = la->config;
u_short i;
- la->delay <<= 1;
- if (__predict_false(la->delay > lc->max))
- la->delay = lc->max;
-
for (i = la->delay; i > 0; i--)
cpu_spinwait();
@@ -141,6 +137,10 @@ lock_delay(struct lock_delay_arg *la)
if (restrict_starvation)
la->delay = lc->base;
}
+
+ la->delay <<= 1;
+ if (__predict_false(la->delay > lc->max))
+ la->delay = lc->max;
}
static u_int
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