[src/trunk]: src/sys/sys Bump MIN_LWP_ALIGNMENT to 64.

[ad <ad%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/5528b39ec9a1
branches:  trunk
changeset: 467058:5528b39ec9a1
user:      ad <ad%NetBSD.org@localhost>
date:      Sun Jan 12 13:19:32 2020 +0000

description:
Bump MIN_LWP_ALIGNMENT to 64.

diffstat:

 sys/sys/param.h |  8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

diffs (31 lines):

diff -r 93f4fd13db36 -r 5528b39ec9a1 sys/sys/param.h
--- a/sys/sys/param.h   Sun Jan 12 13:15:10 2020 +0000
+++ b/sys/sys/param.h   Sun Jan 12 13:19:32 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: param.h,v 1.637 2020/01/10 09:47:19 ad Exp $   */
+/*     $NetBSD: param.h,v 1.638 2020/01/12 13:19:32 ad Exp $   */
 
 /*-
  * Copyright (c) 1982, 1986, 1989, 1993
@@ -196,6 +196,7 @@
 #define        dbtob(x)        ((x) << DEV_BSHIFT)
 #define        btodb(x)        ((x) >> DEV_BSHIFT)
 
+/* Coherency unit: assumed cache line size.  See also MIN_LWP_ALIGNMENT. */
 #ifndef COHERENCY_UNIT
 #define        COHERENCY_UNIT          64
 #endif
@@ -528,10 +529,11 @@
 /*
  * Minimum alignment of "struct lwp" needed by the architecture.
  * This counts when packing a lock byte into a word alongside a
- * pointer to an LWP.
+ * pointer to an LWP.  We need a minimum of 32, but go with 64
+ * to match the cache line size.
  */
 #ifndef MIN_LWP_ALIGNMENT
-#define        MIN_LWP_ALIGNMENT       32
+#define        MIN_LWP_ALIGNMENT       64
 #endif
 #endif /* !__ASSEMBLER__ */