From 739421ac52472d8dd2f23c141d449ff112fbf9b6 Mon Sep 17 00:00:00 2001
From: Justus Winter <4winter@informatik.uni-hamburg.de>
Date: Tue, 30 Sep 2014 09:08:44 +0200
Subject: kern: reduce the size of `struct thread'

Reduce the size of `struct thread' by twelve bytes making it fit into
exactly five cache lines (on 32-bit platforms).

* kern/thread.h (struct thread): Group the state and all flags in a
bitfield.
(TH_EV_WAKE_ACTIVE, TH_EV_STATE): Provide macros that generate keys
for synchronization primitives like `thread_wakeup'.
* kern/thread.c (thread_halt, thread_dowait, thread_suspend): Use the
new keys instead of addresses of fields for the synchronisation.
* kern/ipc_sched.c (thread_handoff): Likewise.
* kern/sched_prim.c (thread_invoke, thread_dispatch): Likewise.
---
 kern/thread.h | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

(limited to 'kern/thread.h')

diff --git a/kern/thread.h b/kern/thread.h
index d088c27..0e85d8c 100644
--- a/kern/thread.h
+++ b/kern/thread.h
@@ -70,6 +70,22 @@ struct thread {
 	task_t		task;		/* Task to which I belong */
 	queue_chain_t	thread_list;	/* list of threads in task */
 
+	/* Flags */
+	/* The flags are grouped here, but documented at the original
+	   position.  */
+	union {
+		struct {
+			unsigned	state:16;
+			unsigned	wake_active:1;
+			unsigned	vm_privilege:1;
+			unsigned	active:1;
+		};
+		event_t	event_key;
+/* These keys can be used with thread_wakeup and friends.  */
+#define TH_EV_WAKE_ACTIVE(t)	((event_t) (&(t)->event_key + 0))
+#define TH_EV_STATE(t)		((event_t) (&(t)->event_key + 1))
+	};
+
 	/* Thread bookkeeping */
 	queue_chain_t	pset_threads;	/* list of all threads in proc set*/
 
@@ -92,9 +108,10 @@ struct thread {
 	kern_return_t	wait_result;	/* outcome of wait -
 					   may be examined by this thread
 					   WITHOUT locking */
-	boolean_t	wake_active;	/* someone is waiting for this
+	/* Defined above */
+	/* boolean_t	wake_active;	   someone is waiting for this
 					   thread to become suspended */
-	int		state;		/* Thread state: */
+	/* int		state;		   Thread state: */
 /*
  *	Thread states [bits or'ed]
  */
@@ -129,7 +146,8 @@ struct thread {
 	/* VM global variables */
 
 	vm_offset_t	recover;	/* page fault recovery (copyin/out) */
-	boolean_t	vm_privilege;	/* Can use reserved memory? */
+	/* Defined above */
+	/* boolean_t	vm_privilege;	   Can use reserved memory? */
 
 	/* User-visible scheduling state */
 	int		user_stop_count;	/* outstanding stops */
@@ -194,7 +212,8 @@ struct thread {
 	timer_elt_data_t depress_timer;	/* timer for priority depression */
 
 	/* Ast/Halt data structures */
-	boolean_t	active;		/* how alive is the thread */
+	/* Defined above */
+	/* boolean_t	active;		   how alive is the thread */
 	int		ast;    	/* ast's needed.  See ast.h */
 
 	/* Processor data structures */
-- 
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