[dpdk-dev] [PATCH v2 2/3] rwlock: add support for HTM lock elision for x86

[Roman Dementiev <roman.dementiev@intel.com>]

This patch adds methods that use hardware memory transactions (HTM) on
fast-path for rwlock (a.k.a. lock elision). Here the methods are implemented
for x86 using Restricted Transactional Memory instructions (Intel(r)
Transactional Synchronization Extensions). The implementation fall-backs to
the normal rwlock if HTM is not available or memory transactions fail. This is
not a replacement for all rwlock usages since not all critical sections
protected by locks are friendly to HTM. For example, an attempt to perform
a HW I/O operation inside a hardware memory transaction always aborts
the transaction since the CPU is not able to roll-back should the transaction
fail. Therefore, hardware transactional locks are not advised to be used around
rte_eth_rx_burst() and rte_eth_tx_burst() calls.

Signed-off-by: Roman Dementiev <roman.dementiev@intel.com>
---
 lib/librte_eal/common/Makefile                     |   4 +-
 .../common/include/arch/ppc_64/rte_rwlock.h        |  38 ++++
 .../common/include/arch/x86/rte_rwlock.h           |  82 ++++++++
 lib/librte_eal/common/include/generic/rte_rwlock.h | 208 +++++++++++++++++++++
 lib/librte_eal/common/include/rte_rwlock.h         | 158 ----------------
 5 files changed, 330 insertions(+), 160 deletions(-)
 create mode 100644 lib/librte_eal/common/include/arch/ppc_64/rte_rwlock.h
 create mode 100644 lib/librte_eal/common/include/arch/x86/rte_rwlock.h
 create mode 100644 lib/librte_eal/common/include/generic/rte_rwlock.h
 delete mode 100644 lib/librte_eal/common/include/rte_rwlock.h

diff --git a/lib/librte_eal/common/Makefile b/lib/librte_eal/common/Makefile
index 3ea3bbf..38772d4 100644
--- a/lib/librte_eal/common/Makefile
+++ b/lib/librte_eal/common/Makefile
@@ -35,7 +35,7 @@ INC := rte_branch_prediction.h rte_common.h
 INC += rte_debug.h rte_eal.h rte_errno.h rte_launch.h rte_lcore.h
 INC += rte_log.h rte_memory.h rte_memzone.h rte_pci.h
 INC += rte_pci_dev_ids.h rte_per_lcore.h rte_random.h
-INC += rte_rwlock.h rte_tailq.h rte_interrupts.h rte_alarm.h
+INC += rte_tailq.h rte_interrupts.h rte_alarm.h
 INC += rte_string_fns.h rte_version.h
 INC += rte_eal_memconfig.h rte_malloc_heap.h
 INC += rte_hexdump.h rte_devargs.h rte_dev.h
@@ -46,7 +46,7 @@ INC += rte_warnings.h
 endif
 
 GENERIC_INC := rte_atomic.h rte_byteorder.h rte_cycles.h rte_prefetch.h
-GENERIC_INC += rte_spinlock.h rte_memcpy.h rte_cpuflags.h
+GENERIC_INC += rte_spinlock.h rte_memcpy.h rte_cpuflags.h rte_rwlock.h
 # defined in mk/arch/$(RTE_ARCH)/rte.vars.mk
 ARCH_DIR ?= $(RTE_ARCH)
 ARCH_INC := $(notdir $(wildcard $(RTE_SDK)/lib/librte_eal/common/include/arch/$(ARCH_DIR)/*.h))
diff --git a/lib/librte_eal/common/include/arch/ppc_64/rte_rwlock.h b/lib/librte_eal/common/include/arch/ppc_64/rte_rwlock.h
new file mode 100644
index 0000000..de8af19
--- /dev/null
+++ b/lib/librte_eal/common/include/arch/ppc_64/rte_rwlock.h
@@ -0,0 +1,38 @@
+#ifndef _RTE_RWLOCK_PPC_64_H_
+#define _RTE_RWLOCK_PPC_64_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "generic/rte_rwlock.h"
+
+static inline void
+rte_rwlock_read_lock_tm(rte_rwlock_t *rwl)
+{
+	rte_rwlock_read_lock(rwl);
+}
+
+static inline void
+rte_rwlock_read_unlock_tm(rte_rwlock_t *rwl)
+{
+	rte_rwlock_read_unlock(rwl);
+}
+
+static inline void
+rte_rwlock_write_lock_tm(rte_rwlock_t *rwl)
+{
+	rte_rwlock_write_lock(rwl);
+}
+
+static inline void
+rte_rwlock_write_unlock_tm(rte_rwlock_t *rwl)
+{
+	rte_rwlock_write_unlock(rwl);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _RTE_RWLOCK_PPC_64_H_ */
diff --git a/lib/librte_eal/common/include/arch/x86/rte_rwlock.h b/lib/librte_eal/common/include/arch/x86/rte_rwlock.h
new file mode 100644
index 0000000..afd1c3c
--- /dev/null
+++ b/lib/librte_eal/common/include/arch/x86/rte_rwlock.h
@@ -0,0 +1,82 @@
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright(c) 2015 Intel Corporation. All rights reserved.
+ *   All rights reserved.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in
+ *       the documentation and/or other materials provided with the
+ *       distribution.
+ *     * Neither the name of Intel Corporation nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _RTE_RWLOCK_X86_64_H_
+#define _RTE_RWLOCK_X86_64_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "generic/rte_rwlock.h"
+#include "rte_spinlock.h"
+
+static inline void
+rte_rwlock_read_lock_tm(rte_rwlock_t *rwl)
+{
+	if (likely(rte_try_tm(&rwl->cnt)))
+		return;
+	rte_rwlock_read_lock(rwl);
+}
+
+static inline void
+rte_rwlock_read_unlock_tm(rte_rwlock_t *rwl)
+{
+	if (unlikely(rwl->cnt))
+		rte_rwlock_read_unlock(rwl);
+	else
+		rte_xend();
+}
+
+static inline void
+rte_rwlock_write_lock_tm(rte_rwlock_t *rwl)
+{
+	if (likely(rte_try_tm(&rwl->cnt)))
+		return;
+	rte_rwlock_write_lock(rwl);
+}
+
+static inline void
+rte_rwlock_write_unlock_tm(rte_rwlock_t *rwl)
+{
+	if (unlikely(rwl->cnt))
+		rte_rwlock_write_unlock(rwl);
+	else
+		rte_xend();
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _RTE_RWLOCK_X86_64_H_ */
diff --git a/lib/librte_eal/common/include/generic/rte_rwlock.h b/lib/librte_eal/common/include/generic/rte_rwlock.h
new file mode 100644
index 0000000..7a0fdc5
--- /dev/null
+++ b/lib/librte_eal/common/include/generic/rte_rwlock.h
@@ -0,0 +1,208 @@
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
+ *   All rights reserved.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in
+ *       the documentation and/or other materials provided with the
+ *       distribution.
+ *     * Neither the name of Intel Corporation nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _RTE_RWLOCK_H_
+#define _RTE_RWLOCK_H_
+
+/**
+ * @file
+ *
+ * RTE Read-Write Locks
+ *
+ * This file defines an API for read-write locks. The lock is used to
+ * protect data that allows multiple readers in parallel, but only
+ * one writer. All readers are blocked until the writer is finished
+ * writing.
+ *
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <rte_common.h>
+#include <rte_atomic.h>
+
+/**
+ * The rte_rwlock_t type.
+ *
+ * cnt is -1 when write lock is held, and > 0 when read locks are held.
+ */
+typedef struct {
+	volatile int32_t cnt; /**< -1 when W lock held, > 0 when R locks held. */
+} rte_rwlock_t;
+
+/**
+ * A static rwlock initializer.
+ */
+#define RTE_RWLOCK_INITIALIZER { 0 }
+
+/**
+ * Initialize the rwlock to an unlocked state.
+ *
+ * @param rwl
+ *   A pointer to the rwlock structure.
+ */
+static inline void
+rte_rwlock_init(rte_rwlock_t *rwl)
+{
+	rwl->cnt = 0;
+}
+
+/**
+ * Take a read lock. Loop until the lock is held.
+ *
+ * @param rwl
+ *   A pointer to a rwlock structure.
+ */
+static inline void
+rte_rwlock_read_lock(rte_rwlock_t *rwl)
+{
+	int32_t x;
+	int success = 0;
+
+	while (success == 0) {
+		x = rwl->cnt;
+		/* write lock is held */
+		if (x < 0) {
+			rte_pause();
+			continue;
+		}
+		success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
+					      x, x + 1);
+	}
+}
+
+/**
+ * Release a read lock.
+ *
+ * @param rwl
+ *   A pointer to the rwlock structure.
+ */
+static inline void
+rte_rwlock_read_unlock(rte_rwlock_t *rwl)
+{
+	rte_atomic32_dec((rte_atomic32_t *)(intptr_t)&rwl->cnt);
+}
+
+/**
+ * Take a write lock. Loop until the lock is held.
+ *
+ * @param rwl
+ *   A pointer to a rwlock structure.
+ */
+static inline void
+rte_rwlock_write_lock(rte_rwlock_t *rwl)
+{
+	int32_t x;
+	int success = 0;
+
+	while (success == 0) {
+		x = rwl->cnt;
+		/* a lock is held */
+		if (x != 0) {
+			rte_pause();
+			continue;
+		}
+		success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
+					      0, -1);
+	}
+}
+
+/**
+ * Release a write lock.
+ *
+ * @param rwl
+ *   A pointer to a rwlock structure.
+ */
+static inline void
+rte_rwlock_write_unlock(rte_rwlock_t *rwl)
+{
+	rte_atomic32_inc((rte_atomic32_t *)(intptr_t)&rwl->cnt);
+}
+
+/**
+ * Try to execute critical section in a hardware memory transaction, if it
+ * fails or not available take a read lock
+ *
+ * NOTE: An attempt to perform a HW I/O operation inside a hardware memory
+ * transaction always aborts the transaction since the CPU is not able to
+ * roll-back should the transaction fail. Therefore, hardware transactional
+ * locks are not advised to be used around rte_eth_rx_burst() and
+ * rte_eth_tx_burst() calls.
+ *
+ * @param rwl
+ *   A pointer to a rwlock structure.
+ */
+static inline void
+rte_rwlock_read_lock_tm(rte_rwlock_t *rwl);
+
+/**
+ * Commit hardware memory transaction or release the read lock if the lock is used as a fall-back
+ *
+ * @param rwl
+ *   A pointer to the rwlock structure.
+ */
+static inline void
+rte_rwlock_read_unlock_tm(rte_rwlock_t *rwl);
+
+/**
+ * Try to execute critical section in a hardware memory transaction, if it
+ * fails or not available take a write lock
+ *
+ * NOTE: An attempt to perform a HW I/O operation inside a hardware memory
+ * transaction always aborts the transaction since the CPU is not able to
+ * roll-back should the transaction fail. Therefore, hardware transactional
+ * locks are not advised to be used around rte_eth_rx_burst() and
+ * rte_eth_tx_burst() calls.
+ *
+ * @param rwl
+ *   A pointer to a rwlock structure.
+ */
+static inline void
+rte_rwlock_write_lock_tm(rte_rwlock_t *rwl);
+
+/**
+ * Commit hardware memory transaction or release the write lock if the lock is used as a fall-back
+ *
+ * @param rwl
+ *   A pointer to a rwlock structure.
+ */
+static inline void
+rte_rwlock_write_unlock_tm(rte_rwlock_t *rwl);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _RTE_RWLOCK_H_ */
diff --git a/lib/librte_eal/common/include/rte_rwlock.h b/lib/librte_eal/common/include/rte_rwlock.h
deleted file mode 100644
index 115731d..0000000
--- a/lib/librte_eal/common/include/rte_rwlock.h
+++ /dev/null
@@ -1,158 +0,0 @@
-/*-
- *   BSD LICENSE
- *
- *   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
- *   All rights reserved.
- *
- *   Redistribution and use in source and binary forms, with or without
- *   modification, are permitted provided that the following conditions
- *   are met:
- *
- *     * Redistributions of source code must retain the above copyright
- *       notice, this list of conditions and the following disclaimer.
- *     * Redistributions in binary form must reproduce the above copyright
- *       notice, this list of conditions and the following disclaimer in
- *       the documentation and/or other materials provided with the
- *       distribution.
- *     * Neither the name of Intel Corporation nor the names of its
- *       contributors may be used to endorse or promote products derived
- *       from this software without specific prior written permission.
- *
- *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#ifndef _RTE_RWLOCK_H_
-#define _RTE_RWLOCK_H_
-
-/**
- * @file
- *
- * RTE Read-Write Locks
- *
- * This file defines an API for read-write locks. The lock is used to
- * protect data that allows multiple readers in parallel, but only
- * one writer. All readers are blocked until the writer is finished
- * writing.
- *
- */
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-#include <rte_common.h>
-#include <rte_atomic.h>
-
-/**
- * The rte_rwlock_t type.
- *
- * cnt is -1 when write lock is held, and > 0 when read locks are held.
- */
-typedef struct {
-	volatile int32_t cnt; /**< -1 when W lock held, > 0 when R locks held. */
-} rte_rwlock_t;
-
-/**
- * A static rwlock initializer.
- */
-#define RTE_RWLOCK_INITIALIZER { 0 }
-
-/**
- * Initialize the rwlock to an unlocked state.
- *
- * @param rwl
- *   A pointer to the rwlock structure.
- */
-static inline void
-rte_rwlock_init(rte_rwlock_t *rwl)
-{
-	rwl->cnt = 0;
-}
-
-/**
- * Take a read lock. Loop until the lock is held.
- *
- * @param rwl
- *   A pointer to a rwlock structure.
- */
-static inline void
-rte_rwlock_read_lock(rte_rwlock_t *rwl)
-{
-	int32_t x;
-	int success = 0;
-
-	while (success == 0) {
-		x = rwl->cnt;
-		/* write lock is held */
-		if (x < 0) {
-			rte_pause();
-			continue;
-		}
-		success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
-					      x, x + 1);
-	}
-}
-
-/**
- * Release a read lock.
- *
- * @param rwl
- *   A pointer to the rwlock structure.
- */
-static inline void
-rte_rwlock_read_unlock(rte_rwlock_t *rwl)
-{
-	rte_atomic32_dec((rte_atomic32_t *)(intptr_t)&rwl->cnt);
-}
-
-/**
- * Take a write lock. Loop until the lock is held.
- *
- * @param rwl
- *   A pointer to a rwlock structure.
- */
-static inline void
-rte_rwlock_write_lock(rte_rwlock_t *rwl)
-{
-	int32_t x;
-	int success = 0;
-
-	while (success == 0) {
-		x = rwl->cnt;
-		/* a lock is held */
-		if (x != 0) {
-			rte_pause();
-			continue;
-		}
-		success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
-					      0, -1);
-	}
-}
-
-/**
- * Release a write lock.
- *
- * @param rwl
- *   A pointer to a rwlock structure.
- */
-static inline void
-rte_rwlock_write_unlock(rte_rwlock_t *rwl)
-{
-	rte_atomic32_inc((rte_atomic32_t *)(intptr_t)&rwl->cnt);
-}
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif /* _RTE_RWLOCK_H_ */
-- 
1.9.5.msysgit.0

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