From 549c7d116fe06cad3a39b38d187daf87ddd22ac7 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Sun, 19 May 2024 09:20:18 -0400
Subject: kernel: sched: Align 'tdq_lock' on cache line size
The lock should be aligned on a cache line boundary so it isn't in a
cache line with other data. This is important for 'tdq_lock' as it is
used by every processor which constantly acquires and releases it. This
alignment can reduce how violently cache lines bounce between processor
local caches.
Signed-off-by: Ian Moffett <ian@osmora.org>
---
sys/kern/kern_sched.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/sys/kern/kern_sched.c b/sys/kern/kern_sched.c
index 0aebf5b..b7e6af5 100644
--- a/sys/kern/kern_sched.c
+++ b/sys/kern/kern_sched.c
@@ -58,7 +58,13 @@ static size_t nthread = 0;
/*
* Thread queue lock - all operations to `td_queue'
* must be done with this lock acquired.
+ *
+ * This lock is aligned on a cache line boundary to ensure
+ * it has its own cacheline to reduce contention. This is
+ * because it is constantly acquired and released on every
+ * processor.
*/
+__cacheline_aligned
static struct spinlock tdq_lock = {0};
/*
--
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