This patch adds methods that use hardware memory transactions (HTM) on fast-path
for spinlocks (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
spinlock if HTM is not available or memory transactions fail. This is not
a replacement for all spinlock usages since not all critical sections protected
by spinlocks 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>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
#endif
+static inline int rte_tm_supported(void)
+{
+ return 0;
+}
+
+static inline void
+rte_spinlock_lock_tm(rte_spinlock_t *sl)
+{
+ rte_spinlock_lock(sl); /* fall-back */
+}
+
+static inline int
+rte_spinlock_trylock_tm(rte_spinlock_t *sl)
+{
+ return rte_spinlock_trylock(sl);
+}
+
+static inline void
+rte_spinlock_unlock_tm(rte_spinlock_t *sl)
+{
+ rte_spinlock_unlock(sl);
+}
+
+static inline void
+rte_spinlock_recursive_lock_tm(rte_spinlock_recursive_t *slr)
+{
+ rte_spinlock_recursive_lock(slr); /* fall-back */
+}
+
+static inline void
+rte_spinlock_recursive_unlock_tm(rte_spinlock_recursive_t *slr)
+{
+ rte_spinlock_recursive_unlock(slr);
+}
+
+static inline int
+rte_spinlock_recursive_trylock_tm(rte_spinlock_recursive_t *slr)
+{
+ return rte_spinlock_recursive_trylock(slr);
+}
+
#ifdef __cplusplus
}
#endif
--- /dev/null
+#ifndef _RTE_RTM_H_
+#define _RTE_RTM_H_ 1
+
+/*
+ * Copyright (c) 2012,2013 Intel Corporation
+ * Author: Andi Kleen
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that: (1) source code distributions
+ * retain the above copyright notice and this paragraph in its entirety, (2)
+ * distributions including binary code include the above copyright notice and
+ * this paragraph in its entirety in the documentation or other materials
+ * provided with the distribution
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+ */
+
+/* Official RTM intrinsics interface matching gcc/icc, but works
+ on older gcc compatible compilers and binutils. */
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+#define RTE_XBEGIN_STARTED (~0u)
+#define RTE_XABORT_EXPLICIT (1 << 0)
+#define RTE_XABORT_RETRY (1 << 1)
+#define RTE_XABORT_CONFLICT (1 << 2)
+#define RTE_XABORT_CAPACITY (1 << 3)
+#define RTE_XABORT_DEBUG (1 << 4)
+#define RTE_XABORT_NESTED (1 << 5)
+#define RTE_XABORT_CODE(x) (((x) >> 24) & 0xff)
+
+static __attribute__((__always_inline__)) inline
+unsigned int rte_xbegin(void)
+{
+ unsigned int ret = RTE_XBEGIN_STARTED;
+
+ asm volatile(".byte 0xc7,0xf8 ; .long 0" : "+a" (ret) :: "memory");
+ return ret;
+}
+
+static __attribute__((__always_inline__)) inline
+void rte_xend(void)
+{
+ asm volatile(".byte 0x0f,0x01,0xd5" ::: "memory");
+}
+
+static __attribute__((__always_inline__)) inline
+void rte_xabort(const unsigned int status)
+{
+ asm volatile(".byte 0xc6,0xf8,%P0" :: "i" (status) : "memory");
+}
+
+static __attribute__((__always_inline__)) inline
+int rte_xtest(void)
+{
+ unsigned char out;
+
+ asm volatile(".byte 0x0f,0x01,0xd6 ; setnz %0" :
+ "=r" (out) :: "memory");
+ return out;
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _RTE_RTM_H_ */
#endif
#include "generic/rte_spinlock.h"
+#include "rte_rtm.h"
+#include "rte_cpuflags.h"
+#include "rte_branch_prediction.h"
+#include "rte_common.h"
+
+#define RTE_RTM_MAX_RETRIES (10)
+#define RTE_XABORT_LOCK_BUSY (0xff)
#ifndef RTE_FORCE_INTRINSICS
static inline void
}
#endif
+static uint8_t rtm_supported; /* cache the flag to avoid the overhead
+ of the rte_cpu_get_flag_enabled function */
+
+static inline void __attribute__((constructor))
+rte_rtm_init(void)
+{
+ rtm_supported = rte_cpu_get_flag_enabled(RTE_CPUFLAG_RTM);
+}
+
+static inline int rte_tm_supported(void)
+{
+ return rtm_supported;
+}
+
+static inline int
+rte_try_tm(volatile int *lock)
+{
+ if (!rtm_supported)
+ return 0;
+
+ int retries = RTE_RTM_MAX_RETRIES;
+
+ while (likely(retries--)) {
+
+ unsigned int status = rte_xbegin();
+
+ if (likely(RTE_XBEGIN_STARTED == status)) {
+ if (unlikely(*lock))
+ rte_xabort(RTE_XABORT_LOCK_BUSY);
+ else
+ return 1;
+ }
+ while (*lock)
+ rte_pause();
+
+ if ((status & RTE_XABORT_EXPLICIT) &&
+ (RTE_XABORT_CODE(status) == RTE_XABORT_LOCK_BUSY))
+ continue;
+
+ if ((status & RTE_XABORT_RETRY) == 0) /* do not retry */
+ break;
+ }
+ return 0;
+}
+
+static inline void
+rte_spinlock_lock_tm(rte_spinlock_t *sl)
+{
+ if (likely(rte_try_tm(&sl->locked)))
+ return;
+
+ rte_spinlock_lock(sl); /* fall-back */
+}
+
+static inline int
+rte_spinlock_trylock_tm(rte_spinlock_t *sl)
+{
+ if (likely(rte_try_tm(&sl->locked)))
+ return 1;
+
+ return rte_spinlock_trylock(sl);
+}
+
+static inline void
+rte_spinlock_unlock_tm(rte_spinlock_t *sl)
+{
+ if (unlikely(sl->locked))
+ rte_spinlock_unlock(sl);
+ else
+ rte_xend();
+}
+
+static inline void
+rte_spinlock_recursive_lock_tm(rte_spinlock_recursive_t *slr)
+{
+ if (likely(rte_try_tm(&slr->sl.locked)))
+ return;
+
+ rte_spinlock_recursive_lock(slr); /* fall-back */
+}
+
+static inline void
+rte_spinlock_recursive_unlock_tm(rte_spinlock_recursive_t *slr)
+{
+ if (unlikely(slr->sl.locked))
+ rte_spinlock_recursive_unlock(slr);
+ else
+ rte_xend();
+}
+
+static inline int
+rte_spinlock_recursive_trylock_tm(rte_spinlock_recursive_t *slr)
+{
+ if (likely(rte_try_tm(&slr->sl.locked)))
+ return 1;
+
+ return rte_spinlock_recursive_trylock(slr);
+}
+
+
#ifdef __cplusplus
}
#endif
return sl->locked;
}
+/**
+ * Test if hardware transactional memory (lock elision) is supported
+ *
+ * @return
+ * 1 if the hardware transactional memory is supported; 0 otherwise.
+ */
+static inline int rte_tm_supported(void);
+
+/**
+ * Try to execute critical section in a hardware memory transaction,
+ * if it fails or not available take the spinlock.
+ *
+ * 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 sl
+ * A pointer to the spinlock.
+ */
+static inline void
+rte_spinlock_lock_tm(rte_spinlock_t *sl);
+
+/**
+ * Commit hardware memory transaction or release the spinlock if
+ * the spinlock is used as a fall-back
+ *
+ * @param sl
+ * A pointer to the spinlock.
+ */
+static inline void
+rte_spinlock_unlock_tm(rte_spinlock_t *sl);
+
+/**
+ * Try to execute critical section in a hardware memory transaction,
+ * if it fails or not available try to take the 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 sl
+ * A pointer to the spinlock.
+ * @return
+ * 1 if the hardware memory transaction is successfully started
+ * or lock is successfully taken; 0 otherwise.
+ */
+static inline int
+rte_spinlock_trylock_tm(rte_spinlock_t *sl);
+
/**
* The rte_spinlock_recursive_t type.
*/
return 1;
}
+
+/**
+ * Try to execute critical section in a hardware memory transaction,
+ * if it fails or not available take the recursive spinlocks
+ *
+ * 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 slr
+ * A pointer to the recursive spinlock.
+ */
+static inline void rte_spinlock_recursive_lock_tm(
+ rte_spinlock_recursive_t *slr);
+
+/**
+ * Commit hardware memory transaction or release the recursive spinlock
+ * if the recursive spinlock is used as a fall-back
+ *
+ * @param slr
+ * A pointer to the recursive spinlock.
+ */
+static inline void rte_spinlock_recursive_unlock_tm(
+ rte_spinlock_recursive_t *slr);
+
+/**
+ * Try to execute critical section in a hardware memory transaction,
+ * if it fails or not available try to take the recursive 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 slr
+ * A pointer to the recursive spinlock.
+ * @return
+ * 1 if the hardware memory transaction is successfully started
+ * or lock is successfully taken; 0 otherwise.
+ */
+static inline int rte_spinlock_recursive_trylock_tm(
+ rte_spinlock_recursive_t *slr);
+
#endif /* _RTE_SPINLOCK_H_ */
git.droids-corp.org / dpdk.git / commitdiff