[PATCH v1 1/4] Benchtests: Add benchtests for pthread_spin_lock and mutex_trylock

[PATCH v1 1/4] Benchtests: Add benchtests for pthread_spin_lock and mutex_trylock

[Noah Goldstein]

Reuses infrastructure from previous pthread_mutex_lock benchmarks to
test other performance sensitive functions.
---
 benchtests/Makefile                           |  8 +++-
 ...utex-locks.c => bench-pthread-lock-base.c} | 20 +++++-----
 benchtests/bench-pthread-mutex-lock.c         | 32 ++++++++++++++++
 benchtests/bench-pthread-mutex-trylock.c      | 37 +++++++++++++++++++
 benchtests/bench-pthread-spinlock.c           | 30 +++++++++++++++
 5 files changed, 115 insertions(+), 12 deletions(-)
 rename benchtests/{bench-pthread-mutex-locks.c => bench-pthread-lock-base.c} (93%)
 create mode 100644 benchtests/bench-pthread-mutex-lock.c
 create mode 100644 benchtests/bench-pthread-mutex-trylock.c
 create mode 100644 benchtests/bench-pthread-spinlock.c

diff --git a/benchtests/Makefile b/benchtests/Makefile
index d99771be74..841997e0a9 100644
--- a/benchtests/Makefile
+++ b/benchtests/Makefile
@@ -103,11 +103,17 @@ endif
 
 bench-pthread := \
   pthread-locks \
-  pthread-mutex-locks \
+  pthread-mutex-lock \
+  pthread-mutex-trylock \
+  pthread-spinlock \
   pthread_once \
   thread_create \
 # bench-pthread
 
+LDLIBS-bench-pthread-mutex-lock += -lm
+LDLIBS-bench-pthread-mutex-trylock += -lm
+LDLIBS-bench-pthread-spinlock += -lm
+
 bench-string := \
   ffs \
   ffsll \
diff --git a/benchtests/bench-pthread-mutex-locks.c b/benchtests/bench-pthread-lock-base.c
similarity index 93%
rename from benchtests/bench-pthread-mutex-locks.c
rename to benchtests/bench-pthread-lock-base.c
index 1685b9dd1f..fac8a12b52 100644
--- a/benchtests/bench-pthread-mutex-locks.c
+++ b/benchtests/bench-pthread-lock-base.c
@@ -1,4 +1,4 @@
-/* Measure mutex_lock for different threads and critical sections.
+/* Measure lock functions for different threads and critical sections.
    Copyright (C) 2022 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
@@ -17,7 +17,6 @@
    <https://www.gnu.org/licenses/>.  */
 
 #define TEST_MAIN
-#define TEST_NAME "pthread-mutex-locks"
 #define TIMEOUT (20 * 60)
 
 #include <stdio.h>
@@ -31,8 +30,8 @@
 #include "bench-timing.h"
 #include "json-lib.h"
 
-static pthread_mutex_t lock;
-static pthread_mutexattr_t attr;
+static bench_lock_t lock;
+static bench_lock_attr_t attr;
 static pthread_barrier_t barrier;
 
 #define START_ITERS 1000
@@ -104,9 +103,9 @@ worker (void *v)
   TIMING_NOW (start);
   while (iters--)
     {
-      pthread_mutex_lock (&lock);
+      LOCK (&lock);
       critical_section (crt_len);
-      pthread_mutex_unlock (&lock);
+      UNLOCK (&lock);
       non_critical_section (non_crt_len);
     }
   TIMING_NOW (stop);
@@ -123,7 +122,7 @@ do_one_test (int num_threads, int crt_len, int non_crt_len, long iters)
   Worker_Params *p, params[num_threads];
   pthread_t threads[num_threads];
 
-  pthread_mutex_init (&lock, &attr);
+  LOCK_INIT (&lock, &attr);
   pthread_barrier_init (&barrier, NULL, num_threads);
 
   for (i = 0; i < num_threads; i++)
@@ -137,7 +136,7 @@ do_one_test (int num_threads, int crt_len, int non_crt_len, long iters)
   for (i = 0; i < num_threads; i++)
     pthread_join (threads[i], NULL);
 
-  pthread_mutex_destroy (&lock);
+  LOCK_DESTROY (&lock);
   pthread_barrier_destroy (&barrier);
 
   mean = 0;
@@ -246,7 +245,7 @@ do_bench (void)
   char name[128];
 
   json_init (&json_ctx, 2, stdout);
-  json_attr_object_begin (&json_ctx, "pthread_mutex_locks");
+  json_attr_object_begin (&json_ctx, TEST_NAME);
 
   /* The thread config begins from 1, and increases by 2x until nprocs.
      We also wants to test over-saturation case (1.25*nprocs).  */
@@ -260,8 +259,7 @@ do_bench (void)
   threads[th_conf++] = nprocs;
   threads[th_conf++] = nprocs + nprocs / 4;
 
-  pthread_mutexattr_init (&attr);
-  pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_ADAPTIVE_NP);
+  LOCK_ATTR_INIT (&attr);
   snprintf (name, sizeof name, "type=adaptive");
 
   for (k = 0; k < (sizeof (non_crt_lens) / sizeof (int)); k++)
diff --git a/benchtests/bench-pthread-mutex-lock.c b/benchtests/bench-pthread-mutex-lock.c
new file mode 100644
index 0000000000..16556d4116
--- /dev/null
+++ b/benchtests/bench-pthread-mutex-lock.c
@@ -0,0 +1,32 @@
+/* Measure mutex_lock for different threads and critical sections.
+   Copyright (C) 2022 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
+   <https://www.gnu.org/licenses/>.  */
+
+#define LOCK(lock) pthread_mutex_lock (lock)
+#define UNLOCK(lock) pthread_mutex_unlock (lock)
+#define LOCK_INIT(lock, attr) pthread_mutex_init (lock, attr)
+#define LOCK_DESTROY(lock) pthread_mutex_destroy (lock)
+#define LOCK_ATTR_INIT(attr)                                                  \
+  pthread_mutexattr_init (attr);                                              \
+  pthread_mutexattr_settype (attr, PTHREAD_MUTEX_ADAPTIVE_NP);
+
+#define bench_lock_t pthread_mutex_t
+#define bench_lock_attr_t pthread_mutexattr_t
+
+#define TEST_NAME "pthread-mutex-lock"
+
+#include "bench-pthread-lock-base.c"
diff --git a/benchtests/bench-pthread-mutex-trylock.c b/benchtests/bench-pthread-mutex-trylock.c
new file mode 100644
index 0000000000..66318f499f
--- /dev/null
+++ b/benchtests/bench-pthread-mutex-trylock.c
@@ -0,0 +1,37 @@
+/* Measure mutex_trylock for different threads and critical sections.
+   Copyright (C) 2022 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
+   <https://www.gnu.org/licenses/>.  */
+
+#define LOCK(lock)                                                            \
+  while (pthread_mutex_trylock (lock) != 0)                                   \
+    {                                                                         \
+      non_critical_section (non_crt_len);                                     \
+    }
+
+#define UNLOCK(lock) pthread_mutex_unlock (lock)
+#define LOCK_INIT(lock, attr) pthread_mutex_init (lock, attr)
+#define LOCK_DESTROY(lock) pthread_mutex_destroy (lock)
+#define LOCK_ATTR_INIT(attr)                                                  \
+  pthread_mutexattr_init (attr);                                              \
+  pthread_mutexattr_settype (attr, PTHREAD_MUTEX_ADAPTIVE_NP);
+
+#define bench_lock_t pthread_mutex_t
+#define bench_lock_attr_t pthread_mutexattr_t
+
+#define TEST_NAME "pthread-mutex-trylock"
+
+#include "bench-pthread-lock-base.c"
diff --git a/benchtests/bench-pthread-spinlock.c b/benchtests/bench-pthread-spinlock.c
new file mode 100644
index 0000000000..2174933d6b
--- /dev/null
+++ b/benchtests/bench-pthread-spinlock.c
@@ -0,0 +1,30 @@
+/* Measure mutex_trylock for different threads and critical sections.
+   Copyright (C) 2022 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
+   <https://www.gnu.org/licenses/>.  */
+
+#define LOCK(lock) pthread_spin_lock (lock)
+#define UNLOCK(lock) pthread_spin_unlock (lock)
+#define LOCK_INIT(lock, attr) pthread_spin_init (lock, *(attr))
+#define LOCK_DESTROY(lock) pthread_spin_destroy (lock)
+#define LOCK_ATTR_INIT(attr) *(attr) = 0
+
+#define bench_lock_t pthread_spinlock_t
+#define bench_lock_attr_t int
+
+#define TEST_NAME "pthread-spin-lock"
+
+#include "bench-pthread-lock-base.c"
-- 
2.34.1

[PATCH v1 2/4] nptl: Continue use arch prefered atomic exchange in spinlock loop

[Noah Goldstein]

Despite using the preferred atomic exchange in the initial check, the
loop was unconditionally using CAS which is not desired on some
architectures (those that didn't set `ATOMIC_EXCHANGE_USES_CAS`).

No meaningful perf changes measured on broadwell but still seems like
a reasonable change.

Full check passes on x86-64.
---
 nptl/pthread_spin_lock.c | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/nptl/pthread_spin_lock.c b/nptl/pthread_spin_lock.c
index 19d1759f9a..1bdd6e2048 100644
--- a/nptl/pthread_spin_lock.c
+++ b/nptl/pthread_spin_lock.c
@@ -20,6 +20,20 @@
 #include "pthreadP.h"
 #include <shlib-compat.h>
 
+#if ATOMIC_EXCHANGE_USES_CAS
+/* Try to acquire the lock with a CAS instruction as this architecture
+   has no exchange instruction.  The acquisition succeeds if the lock is not
+   acquired.  */
+#  define pthread_spin_lock_grab_lock(mem, val, c) \
+    atomic_compare_exchange_weak_acquire (lock, &val, 1))
+#else
+/* Try to acquire the lock with an exchange instruction as this architecture
+   has such an instruction and we assume it is faster than a CAS.
+   The acquisition succeeds if the lock is not in an acquired state.  */
+#  define pthread_spin_lock_grab_lock(mem, val, c) \
+    (atomic_exchange_acquire (lock, 1) == 0)
+#endif
+
 int
 __pthread_spin_lock (pthread_spinlock_t *lock)
 {
@@ -36,19 +50,8 @@ __pthread_spin_lock (pthread_spinlock_t *lock)
      We use acquire MO to synchronize-with the release MO store in
      pthread_spin_unlock, and thus ensure that prior critical sections
      happen-before this critical section.  */
-#if ! ATOMIC_EXCHANGE_USES_CAS
-  /* Try to acquire the lock with an exchange instruction as this architecture
-     has such an instruction and we assume it is faster than a CAS.
-     The acquisition succeeds if the lock is not in an acquired state.  */
-  if (__glibc_likely (atomic_exchange_acquire (lock, 1) == 0))
+  if (__glibc_likely (pthread_spin_lock_grab_lock (lock, &val, 1)))
     return 0;
-#else
-  /* Try to acquire the lock with a CAS instruction as this architecture
-     has no exchange instruction.  The acquisition succeeds if the lock is not
-     acquired.  */
-  if (__glibc_likely (atomic_compare_exchange_weak_acquire (lock, &val, 1)))
-    return 0;
-#endif
 
   do
     {
@@ -75,7 +78,7 @@ __pthread_spin_lock (pthread_spinlock_t *lock)
       /* We need acquire memory order here for the same reason as mentioned
 	 for the first try to lock the spinlock.  */
     }
-  while (!atomic_compare_exchange_weak_acquire (lock, &val, 1));
+  while (!pthread_spin_lock_grab_lock (lock, &val, 1));
 
   return 0;
 }
-- 
2.34.1