From cf558f10a7abeda01e8e79a571df6af5c79bdd5b Mon Sep 17 00:00:00 2001
From: Mateusz Guzik <mjg@FreeBSD.org>
Date: Wed, 6 Sep 2017 20:32:49 +0000
Subject: [PATCH] Introduce __read_frequently

While __read_mostly groups variables together, their placement is not
specified. In particular 2 frequently used variables can end up in
different lines.

This annotation is only expected to be used for variables read all the time,
e.g. on each syscall entry.

MFC after:	1 week
---
 sys/conf/ldscript.amd64 | 4 ++++
 sys/sys/systm.h         | 1 +
 2 files changed, 5 insertions(+)

diff --git a/sys/conf/ldscript.amd64 b/sys/conf/ldscript.amd64
index b2ca347a7c85..43fde20370bc 100644
--- a/sys/conf/ldscript.amd64
+++ b/sys/conf/ldscript.amd64
@@ -146,6 +146,10 @@ SECTIONS
   . = DATA_SEGMENT_RELRO_END (24, .);
   .got.plt        : { *(.got.plt) }
   . = ALIGN(64);
+  .data.read_frequently :
+  {
+    *(.data.read_frequently)
+  }
   .data.read_mostly :
   {
     *(.data.read_mostly)
diff --git a/sys/sys/systm.h b/sys/sys/systm.h
index b70a0d9ac690..30a25ef9620d 100644
--- a/sys/sys/systm.h
+++ b/sys/sys/systm.h
@@ -138,6 +138,7 @@ void	kassert_panic(const char *fmt, ...)  __printflike(1, 2);
  * Align variables.
  */
 #define	__read_mostly		__section(".data.read_mostly")
+#define	__read_frequently	__section(".data.read_frequently")
 #define	__exclusive_cache_line	__aligned(CACHE_LINE_SIZE) \
 				    __section(".data.exclusive_cache_line")
 /*