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Date:      Thu, 3 May 2012 09:17:31 +0000 (UTC)
From:      David Xu <davidxu@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r234947 - head/lib/libthr/thread
Message-ID:  <201205030917.q439HVln029728@svn.freebsd.org>

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Author: davidxu
Date: Thu May  3 09:17:31 2012
New Revision: 234947
URL: http://svn.freebsd.org/changeset/base/234947

Log:
  MFp4:
  Enqueue thread in LIFO, this can cause starvation, but it gives better
  performance. Use _thr_queuefifo to control the frequency of FIFO vs LIFO,
  you can use environment string LIBPTHREAD_QUEUE_FIFO to configure the
  variable.

Modified:
  head/lib/libthr/thread/thr_init.c
  head/lib/libthr/thread/thr_private.h
  head/lib/libthr/thread/thr_sleepq.c

Modified: head/lib/libthr/thread/thr_init.c
==============================================================================
--- head/lib/libthr/thread/thr_init.c	Thu May  3 08:56:43 2012	(r234946)
+++ head/lib/libthr/thread/thr_init.c	Thu May  3 09:17:31 2012	(r234947)
@@ -112,6 +112,7 @@ size_t		_thr_stack_initial = THR_STACK_I
 int		_thr_page_size;
 int		_thr_spinloops;
 int		_thr_yieldloops;
+int		_thr_queuefifo = 4;
 int		_gc_count;
 struct umutex	_mutex_static_lock = DEFAULT_UMUTEX;
 struct umutex	_cond_static_lock = DEFAULT_UMUTEX;
@@ -470,6 +471,9 @@ init_private(void)
 		env = getenv("LIBPTHREAD_YIELDLOOPS");
 		if (env)
 			_thr_yieldloops = atoi(env);
+		env = getenv("LIBPTHREAD_QUEUE_FIFO");
+		if (env)
+			_thr_queuefifo = atoi(env);
 		TAILQ_INIT(&_thr_atfork_list);
 	}
 	init_once = 1;

Modified: head/lib/libthr/thread/thr_private.h
==============================================================================
--- head/lib/libthr/thread/thr_private.h	Thu May  3 08:56:43 2012	(r234946)
+++ head/lib/libthr/thread/thr_private.h	Thu May  3 09:17:31 2012	(r234947)
@@ -710,6 +710,7 @@ extern size_t	_thr_stack_initial __hidde
 extern int	_thr_page_size __hidden;
 extern int	_thr_spinloops __hidden;
 extern int	_thr_yieldloops __hidden;
+extern int	_thr_queuefifo __hidden;
 
 /* Garbage thread count. */
 extern int	_gc_count __hidden;

Modified: head/lib/libthr/thread/thr_sleepq.c
==============================================================================
--- head/lib/libthr/thread/thr_sleepq.c	Thu May  3 08:56:43 2012	(r234946)
+++ head/lib/libthr/thread/thr_sleepq.c	Thu May  3 09:17:31 2012	(r234947)
@@ -39,6 +39,7 @@
 
 struct sleepqueue_chain {
 	struct umutex		sc_lock;
+	int			sc_enqcnt;
 	LIST_HEAD(, sleepqueue) sc_queues;
 	int			sc_type;
 };
@@ -124,7 +125,10 @@ _sleepq_add(void *wchan, struct pthread 
 	}
 	td->sleepqueue = NULL;
 	td->wchan = wchan;
-	TAILQ_INSERT_TAIL(&sq->sq_blocked, td, wle);
+	if (((++sc->sc_enqcnt << _thr_queuefifo) & 0xff) != 0)
+		TAILQ_INSERT_HEAD(&sq->sq_blocked, td, wle);
+	else
+		TAILQ_INSERT_TAIL(&sq->sq_blocked, td, wle);
 }
 
 int



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