[PATCH 1/3] Tunables: Add tunables of spin count for adaptive spin mutex

[Kemi Wang <kemi dot wang at intel dot com>]

This patch does not have any functionality change, we only provide a spin
count tunes for pthread adaptive spin mutex. The tunable
glibc.mutex.spin_count tunes can be used by system adminstrator to squeeze
system performance according to different hardware capability and workload
model.

This is the preparation work for the next patch, in which the way of
adaptive spin would be changed from an expensive cmpxchg to read while
spinning.

   * elf/dl-tunables.list: Add glibc.mutex.spin_count entry.
   * manual/tunables.texi: Add glibc.mutex.spin_count description.
   * nptl/Makefile: Add mutex-conf.c for compilation.
   * nptl/mutex-conf.h: New file.
   * nptl/mutex-conf.c: New file.

Suggested-by: Andi Kleen <andi.kleen@intel.com>
Signed-off-by: Kemi Wang <kemi.wang@intel.com>
---
 ChangeLog            | 10 ++++++-
 elf/dl-tunables.list | 10 +++++++
 manual/tunables.texi | 17 ++++++++++++
 nptl/Makefile        |  3 +-
 nptl/mutex-conf.c    | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 nptl/mutex-conf.h    | 31 +++++++++++++++++++++
 6 files changed, 147 insertions(+), 2 deletions(-)
 create mode 100644 nptl/mutex-conf.c
 create mode 100644 nptl/mutex-conf.h

diff --git a/ChangeLog b/ChangeLog
index 1f98425..472657c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,13 @@
-2018-03-29  Florian Weimer  <fweimer@redhat.com>
+2018-03-30 Kemi Wang <kemi.wang@intel.com>
+
+	* elf/dl-tunables.list: Add glibc.mutex.spin_count entry.
+	* manual/tunables.texi: Add glibc.mutex.spin_count description.
+	* nptl/Makefile: Add mutex-conf.c for compilation.
+	* nptl/mutex-conf.h: New file.
+	* nptl/mutex-conf.c: New file.
+	* nptl/Makefile: Add new file compilation.
 
+2018-03-29  Florian Weimer  <fweimer@redhat.com>
 	* sysdeps/unix/sysv/linux/i386/tst-bz21269.c (do_test): Also
 	capture SIGBUS.
 
diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list
index 1f8ecb8..0c27c14 100644
--- a/elf/dl-tunables.list
+++ b/elf/dl-tunables.list
@@ -121,4 +121,14 @@ glibc {
       default: 3
     }
   }
+
+  mutex {
+	  spin_count {
+		  type: INT_32
+		  minval: 0
+		  maxval: 30000
+		  env_alias: LD_SPIN_COUNT
+		  default: 1000
+	  }
+  }
 }
diff --git a/manual/tunables.texi b/manual/tunables.texi
index be33c9f..9c6a9f1 100644
--- a/manual/tunables.texi
+++ b/manual/tunables.texi
@@ -281,6 +281,23 @@ of try lock attempts.
 The default value of this tunable is @samp{3}.
 @end deftp
 
+@node Pthread Mutex Tunables
+@section Pthread Mutex Tunables
+@cindex pthread mutex tunables
+
+@deftp {Tunable namespace} glibc.mutex
+Behavior of ptherad mutex can be tuned to acquire performance improvement
+according to specific hardware capablity and workload character by setting
+the following tunables in the @code{mutex} namespace.
+@end deftp
+
+@deftp Tunable glibc.mutex.spin_count
+The @code{glibc.mutex.spin_count} tunable set the maximum times the thread
+should spin on the lock before going to sleep.
+
+The default value of this tunable is @samp{1000}.
+@end deftp
+
 @node Hardware Capability Tunables
 @section Hardware Capability Tunables
 @cindex hardware capability tunables
diff --git a/nptl/Makefile b/nptl/Makefile
index 94be92c..5edacea 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -139,7 +139,8 @@ libpthread-routines = nptl-init vars events version pt-interp \
 		      pthread_mutex_getprioceiling \
 		      pthread_mutex_setprioceiling \
 		      pthread_setname pthread_getname \
-		      pthread_setattr_default_np pthread_getattr_default_np
+		      pthread_setattr_default_np pthread_getattr_default_np \
+		      mutex-conf
 #		      pthread_setuid pthread_seteuid pthread_setreuid \
 #		      pthread_setresuid \
 #		      pthread_setgid pthread_setegid pthread_setregid \
diff --git a/nptl/mutex-conf.c b/nptl/mutex-conf.c
new file mode 100644
index 0000000..f4ffd6d
--- /dev/null
+++ b/nptl/mutex-conf.c
@@ -0,0 +1,78 @@
+/* mutex-conf.c: Pthread mutex tunable parameters.
+   Copyright (C) 2013-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include <pthreadP.h>
+#include <init-arch.h>
+#include <mutex-conf.h>
+#include <unistd.h>
+
+#if HAVE_TUNABLES
+# define TUNABLE_NAMESPACE mutex
+#endif
+#include <elf/dl-tunables.h>
+
+
+struct mutex_config __mutex_aconf =
+  {
+	  /* The maximum times a thread spin on the lock before
+	   * going to sleep */
+	  .spin_count = 1000,
+  };
+
+#if HAVE_TUNABLES
+#define TUNABLE_CALLBACK_FNDECL(__name, __type)			\
+static inline void						\
+__always_inline							\
+do_set_mutex_ ## __name (__type value)			\
+{								\
+  __mutex_aconf.__name = value;				\
+}								\
+void								\
+TUNABLE_CALLBACK (set_mutex_ ## __name) (tunable_val_t *valp) \
+{								\
+  __type value = (__type) (valp)->numval;			\
+  do_set_mutex_ ## __name (value);				\
+}
+
+TUNABLE_CALLBACK_FNDECL (spin_count, int32_t);
+#endif
+
+static void
+mutex_tunables_init (int argc __attribute__ ((unused)),
+			      char **argv  __attribute__ ((unused)),
+					      char **environ)
+{
+#if HAVE_TUNABLES
+
+	TUNABLE_GET (spin_count, int32_t,
+			TUNABLE_CALLBACK (set_mutex_spin_count));
+#endif
+}
+
+#ifdef SHARED
+# define INIT_SECTION ".init_array"
+#else
+# define INIT_SECTION ".preinit_array"
+#endif
+
+void (*const __pthread_mutex_tunables_init_array []) (int, char **, char **)
+  __attribute__ ((section (INIT_SECTION), aligned (sizeof (void *)))) =
+{
+  &mutex_tunables_init
+};
diff --git a/nptl/mutex-conf.h b/nptl/mutex-conf.h
new file mode 100644
index 0000000..babefe3
--- /dev/null
+++ b/nptl/mutex-conf.h
@@ -0,0 +1,31 @@
+/* mutex-conf.h: Pthread mutex tunable parameters.
+   Copyright (C) 2013-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+#ifndef _MUTEX_CONF_H
+#define _MUTEX_CONF_H 1
+
+#include <pthread.h>
+#include <time.h>
+
+struct mutex_config
+{
+  int spin_count;
+};
+
+extern struct mutex_config __mutex_aconf attribute_hidden;
+
+#endif
-- 
2.7.4