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From: Mateusz Guzik <mjg@FreeBSD.org>
Date: Wed, 6 Sep 2017 20:32:49 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r323235 - in head/sys: conf sys
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Author: mjg
Date: Wed Sep  6 20:32:49 2017
New Revision: 323235
URL: https://svnweb.freebsd.org/changeset/base/323235

Log:
  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

Modified:
  head/sys/conf/ldscript.amd64
  head/sys/sys/systm.h

Modified: head/sys/conf/ldscript.amd64
==============================================================================
--- head/sys/conf/ldscript.amd64	Wed Sep  6 20:28:18 2017	(r323234)
+++ head/sys/conf/ldscript.amd64	Wed Sep  6 20:32:49 2017	(r323235)
@@ -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)

Modified: head/sys/sys/systm.h
==============================================================================
--- head/sys/sys/systm.h	Wed Sep  6 20:28:18 2017	(r323234)
+++ head/sys/sys/systm.h	Wed Sep  6 20:32:49 2017	(r323235)
@@ -138,6 +138,7 @@ void	kassert_panic(const char *fmt, ...)  __printflike
  * 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")
 /*