Author: mjg
Date: Fri Jan 27 14:53:09 2017
New Revision: 312888
URL: https://svnweb.freebsd.org/changeset/base/312888
Log:
Introduce __read_mostly and __exclusive_cache_line macros.
The intended use is to annotate frequently used globals which either rarely
change (and thus can be grouped in the same cacheline) or are an atomic
counter
(which means it may benefit from being the only variable in the cacheline).
Linker script support is provided only for amd64. Architectures without it
risk
having other variables put in, i.e. as if they were not annotated. This is
harmless from correctness point of view.
Reviewed by: bde (previous version)
MFC after: 1 month
Modified:
head/sys/compat/linuxkpi/common/include/linux/compiler.h
head/sys/conf/ldscript.amd64
head/sys/dev/drm2/drm_os_freebsd.h
head/sys/sys/systm.h
Modified: head/sys/compat/linuxkpi/common/include/linux/compiler.h
==============================================================================
--- head/sys/compat/linuxkpi/common/include/linux/compiler.h Fri Jan 27
14:17:48 2017 (r312887)
+++ head/sys/compat/linuxkpi/common/include/linux/compiler.h Fri Jan 27
14:53:09 2017 (r312888)
@@ -67,7 +67,6 @@
#define typeof(x) __typeof(x)
#define uninitialized_var(x) x = x
-#define __read_mostly __attribute__((__section__(".data.read_mostly")))
#define __always_unused __unused
#define __must_check __result_use_check
Modified: head/sys/conf/ldscript.amd64
==============================================================================
--- head/sys/conf/ldscript.amd64 Fri Jan 27 14:17:48 2017
(r312887)
+++ head/sys/conf/ldscript.amd64 Fri Jan 27 14:53:09 2017
(r312888)
@@ -145,6 +145,17 @@ SECTIONS
.got : { *(.got) }
. = DATA_SEGMENT_RELRO_END (24, .);
.got.plt : { *(.got.plt) }
+ . = ALIGN(64);
+ .data.read_mostly :
+ {
+ *(.data.read_mostly)
+ }
+ . = ALIGN(64);
+ .data.exclusive_cache_line :
+ {
+ *(.data.exclusive_cache_line)
+ }
+ . = ALIGN(64);
.data :
{
*(.data .data.* .gnu.linkonce.d.*)
Modified: head/sys/dev/drm2/drm_os_freebsd.h
==============================================================================
--- head/sys/dev/drm2/drm_os_freebsd.h Fri Jan 27 14:17:48 2017
(r312887)
+++ head/sys/dev/drm2/drm_os_freebsd.h Fri Jan 27 14:53:09 2017
(r312888)
@@ -80,7 +80,6 @@ typedef void irqreturn_t;
#define __init
#define __exit
-#define __read_mostly
#define BUILD_BUG_ON(x) CTASSERT(!(x))
#define BUILD_BUG_ON_NOT_POWER_OF_2(x)
Modified: head/sys/sys/systm.h
==============================================================================
--- head/sys/sys/systm.h Fri Jan 27 14:17:48 2017 (r312887)
+++ head/sys/sys/systm.h Fri Jan 27 14:53:09 2017 (r312888)
@@ -129,6 +129,12 @@ void kassert_panic(const char *fmt, ...)
#define SCHEDULER_STOPPED() __predict_false(curthread->td_stopsched)
/*
+ * Align variables.
+ */
+#define __read_mostly __section(".data.read_mostly")
+#define __exclusive_cache_line __aligned(CACHE_LINE_SIZE) \
+ __section(".data.exclusive_cache_line")
+/*
* XXX the hints declarations are even more misplaced than most declarations
* in this file, since they are needed in one file (per arch) and only used
* in two files.
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