From: Roman Dementiev Date: Fri, 19 Jun 2015 11:08:21 +0000 (+0200) Subject: spinlock: add HTM lock elision for x86 X-Git-Tag: spdx-start~9039 X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=ba7468997ea6dd7a019ea00367c56867eb6431e9;p=dpdk.git spinlock: add HTM lock elision for x86 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 Acked-by: Bruce Richardson --- diff --git a/lib/librte_eal/common/include/arch/ppc_64/rte_spinlock.h b/lib/librte_eal/common/include/arch/ppc_64/rte_spinlock.h index cf8b81ad3f..3336435bc2 100644 --- a/lib/librte_eal/common/include/arch/ppc_64/rte_spinlock.h +++ b/lib/librte_eal/common/include/arch/ppc_64/rte_spinlock.h @@ -66,6 +66,47 @@ rte_spinlock_trylock(rte_spinlock_t *sl) #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 diff --git a/lib/librte_eal/common/include/arch/x86/rte_rtm.h b/lib/librte_eal/common/include/arch/x86/rte_rtm.h new file mode 100644 index 0000000000..d9356419af --- /dev/null +++ b/lib/librte_eal/common/include/arch/x86/rte_rtm.h @@ -0,0 +1,73 @@ +#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_ */ diff --git a/lib/librte_eal/common/include/arch/x86/rte_spinlock.h b/lib/librte_eal/common/include/arch/x86/rte_spinlock.h index 54fba95774..20ef0a794a 100644 --- a/lib/librte_eal/common/include/arch/x86/rte_spinlock.h +++ b/lib/librte_eal/common/include/arch/x86/rte_spinlock.h @@ -39,6 +39,13 @@ extern "C" { #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 @@ -87,6 +94,106 @@ rte_spinlock_trylock (rte_spinlock_t *sl) } #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 diff --git a/lib/librte_eal/common/include/generic/rte_spinlock.h b/lib/librte_eal/common/include/generic/rte_spinlock.h index c7fb0dfa29..4e0a3c3018 100644 --- a/lib/librte_eal/common/include/generic/rte_spinlock.h +++ b/lib/librte_eal/common/include/generic/rte_spinlock.h @@ -144,6 +144,59 @@ static inline int rte_spinlock_is_locked (rte_spinlock_t *sl) 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. */ @@ -223,4 +276,50 @@ static inline int rte_spinlock_recursive_trylock(rte_spinlock_recursive_t *slr) 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_ */