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([10.123.72.192]) by FMSMGA003.fm.intel.com with ESMTP; 10 Jan 2019 13:02:32 -0800 From: Gage Eads To: dev@dpdk.org Cc: olivier.matz@6wind.com, arybchenko@solarflare.com, bruce.richardson@intel.com, konstantin.ananyev@intel.com Date: Thu, 10 Jan 2019 15:01:17 -0600 Message-Id: <20190110210122.24889-2-gage.eads@intel.com> X-Mailer: git-send-email 2.13.6 In-Reply-To: <20190110210122.24889-1-gage.eads@intel.com> References: <20190110210122.24889-1-gage.eads@intel.com> Subject: [dpdk-dev] [PATCH 1/6] ring: change head and tail to pointer-width size X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 10 Jan 2019 21:02:34 -0000 For 64-bit architectures, doubling the head and tail index widths greatly increases the time it takes for them to wrap-around (with current CPU speeds, it won't happen within the author's lifetime). This is important in avoiding the ABA problem -- in which a thread mistakes reading the same tail index in two accesses to mean that the ring was not modified in the intervening time -- in the upcoming non-blocking ring implementation. Using a 64-bit index makes the possibility of this occurring effectively zero. I tested this commit's performance impact with an x86_64 build on a dual-socket Xeon E5-2699 v4 using ring_perf_autotest, and the change made no significant difference -- the few differences appear to be system noise. (The test ran on isolcpus cores using a tickless scheduler, but some variation was stll observed.) Each test was run three times and the results were averaged: | 64b head/tail cycle cost minus Test | 32b head/tail cycle cost ------------------------------------------------------------------ SP/SC single enq/dequeue | 0.33 MP/MC single enq/dequeue | 0.00 SP/SC burst enq/dequeue (size 8) | 0.00 MP/MC burst enq/dequeue (size 8) | 1.00 SP/SC burst enq/dequeue (size 32) | 0.00 MP/MC burst enq/dequeue (size 32) | -1.00 SC empty dequeue | 0.01 MC empty dequeue | 0.00 Single lcore: SP/SC bulk enq/dequeue (size 8) | -0.36 MP/MC bulk enq/dequeue (size 8) | 0.99 SP/SC bulk enq/dequeue (size 32) | -0.40 MP/MC bulk enq/dequeue (size 32) | -0.57 Two physical cores: SP/SC bulk enq/dequeue (size 8) | -0.49 MP/MC bulk enq/dequeue (size 8) | 0.19 SP/SC bulk enq/dequeue (size 32) | -0.28 MP/MC bulk enq/dequeue (size 32) | -0.62 Two NUMA nodes: SP/SC bulk enq/dequeue (size 8) | 3.25 MP/MC bulk enq/dequeue (size 8) | 1.87 SP/SC bulk enq/dequeue (size 32) | -0.44 MP/MC bulk enq/dequeue (size 32) | -1.10 An earlier version of this patch changed the head and tail indexes to uint64_t, but that caused a performance drop on 32-bit builds. With uintptr_t, no performance difference is observed on an i686 build. Signed-off-by: Gage Eads --- lib/librte_eventdev/rte_event_ring.h | 6 +++--- lib/librte_ring/rte_ring.c | 10 +++++----- lib/librte_ring/rte_ring.h | 20 ++++++++++---------- lib/librte_ring/rte_ring_generic.h | 16 +++++++++------- 4 files changed, 27 insertions(+), 25 deletions(-) diff --git a/lib/librte_eventdev/rte_event_ring.h b/lib/librte_eventdev/rte_event_ring.h index 827a3209e..eae70f904 100644 --- a/lib/librte_eventdev/rte_event_ring.h +++ b/lib/librte_eventdev/rte_event_ring.h @@ -1,5 +1,5 @@ /* SPDX-License-Identifier: BSD-3-Clause - * Copyright(c) 2016-2017 Intel Corporation + * Copyright(c) 2016-2019 Intel Corporation */ /** @@ -88,7 +88,7 @@ rte_event_ring_enqueue_burst(struct rte_event_ring *r, const struct rte_event *events, unsigned int n, uint16_t *free_space) { - uint32_t prod_head, prod_next; + uintptr_t prod_head, prod_next; uint32_t free_entries; n = __rte_ring_move_prod_head(&r->r, r->r.prod.single, n, @@ -129,7 +129,7 @@ rte_event_ring_dequeue_burst(struct rte_event_ring *r, struct rte_event *events, unsigned int n, uint16_t *available) { - uint32_t cons_head, cons_next; + uintptr_t cons_head, cons_next; uint32_t entries; n = __rte_ring_move_cons_head(&r->r, r->r.cons.single, n, diff --git a/lib/librte_ring/rte_ring.c b/lib/librte_ring/rte_ring.c index d215acecc..b15ee0eb3 100644 --- a/lib/librte_ring/rte_ring.c +++ b/lib/librte_ring/rte_ring.c @@ -1,6 +1,6 @@ /* SPDX-License-Identifier: BSD-3-Clause * - * Copyright (c) 2010-2015 Intel Corporation + * Copyright (c) 2010-2019 Intel Corporation * Copyright (c) 2007,2008 Kip Macy kmacy@freebsd.org * All rights reserved. * Derived from FreeBSD's bufring.h @@ -227,10 +227,10 @@ rte_ring_dump(FILE *f, const struct rte_ring *r) fprintf(f, " flags=%x\n", r->flags); fprintf(f, " size=%"PRIu32"\n", r->size); fprintf(f, " capacity=%"PRIu32"\n", r->capacity); - fprintf(f, " ct=%"PRIu32"\n", r->cons.tail); - fprintf(f, " ch=%"PRIu32"\n", r->cons.head); - fprintf(f, " pt=%"PRIu32"\n", r->prod.tail); - fprintf(f, " ph=%"PRIu32"\n", r->prod.head); + fprintf(f, " ct=%"PRIuPTR"\n", r->cons.tail); + fprintf(f, " ch=%"PRIuPTR"\n", r->cons.head); + fprintf(f, " pt=%"PRIuPTR"\n", r->prod.tail); + fprintf(f, " ph=%"PRIuPTR"\n", r->prod.head); fprintf(f, " used=%u\n", rte_ring_count(r)); fprintf(f, " avail=%u\n", rte_ring_free_count(r)); } diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h index af5444a9f..12af64e13 100644 --- a/lib/librte_ring/rte_ring.h +++ b/lib/librte_ring/rte_ring.h @@ -1,6 +1,6 @@ /* SPDX-License-Identifier: BSD-3-Clause * - * Copyright (c) 2010-2017 Intel Corporation + * Copyright (c) 2010-2019 Intel Corporation * Copyright (c) 2007-2009 Kip Macy kmacy@freebsd.org * All rights reserved. * Derived from FreeBSD's bufring.h @@ -65,8 +65,8 @@ struct rte_memzone; /* forward declaration, so as not to require memzone.h */ /* structure to hold a pair of head/tail values and other metadata */ struct rte_ring_headtail { - volatile uint32_t head; /**< Prod/consumer head. */ - volatile uint32_t tail; /**< Prod/consumer tail. */ + volatile uintptr_t head; /**< Prod/consumer head. */ + volatile uintptr_t tail; /**< Prod/consumer tail. */ uint32_t single; /**< True if single prod/cons */ }; @@ -242,7 +242,7 @@ void rte_ring_dump(FILE *f, const struct rte_ring *r); #define ENQUEUE_PTRS(r, ring_start, prod_head, obj_table, n, obj_type) do { \ unsigned int i; \ const uint32_t size = (r)->size; \ - uint32_t idx = prod_head & (r)->mask; \ + uintptr_t idx = prod_head & (r)->mask; \ obj_type *ring = (obj_type *)ring_start; \ if (likely(idx + n < size)) { \ for (i = 0; i < (n & ((~(unsigned)0x3))); i+=4, idx+=4) { \ @@ -272,7 +272,7 @@ void rte_ring_dump(FILE *f, const struct rte_ring *r); * single and multi consumer dequeue functions */ #define DEQUEUE_PTRS(r, ring_start, cons_head, obj_table, n, obj_type) do { \ unsigned int i; \ - uint32_t idx = cons_head & (r)->mask; \ + uintptr_t idx = cons_head & (r)->mask; \ const uint32_t size = (r)->size; \ obj_type *ring = (obj_type *)ring_start; \ if (likely(idx + n < size)) { \ @@ -338,7 +338,7 @@ __rte_ring_do_enqueue(struct rte_ring *r, void * const *obj_table, unsigned int n, enum rte_ring_queue_behavior behavior, unsigned int is_sp, unsigned int *free_space) { - uint32_t prod_head, prod_next; + uintptr_t prod_head, prod_next; uint32_t free_entries; n = __rte_ring_move_prod_head(r, is_sp, n, behavior, @@ -380,7 +380,7 @@ __rte_ring_do_dequeue(struct rte_ring *r, void **obj_table, unsigned int n, enum rte_ring_queue_behavior behavior, unsigned int is_sc, unsigned int *available) { - uint32_t cons_head, cons_next; + uintptr_t cons_head, cons_next; uint32_t entries; n = __rte_ring_move_cons_head(r, (int)is_sc, n, behavior, @@ -681,9 +681,9 @@ rte_ring_dequeue(struct rte_ring *r, void **obj_p) static inline unsigned rte_ring_count(const struct rte_ring *r) { - uint32_t prod_tail = r->prod.tail; - uint32_t cons_tail = r->cons.tail; - uint32_t count = (prod_tail - cons_tail) & r->mask; + uintptr_t prod_tail = r->prod.tail; + uintptr_t cons_tail = r->cons.tail; + uintptr_t count = (prod_tail - cons_tail) & r->mask; return (count > r->capacity) ? r->capacity : count; } diff --git a/lib/librte_ring/rte_ring_generic.h b/lib/librte_ring/rte_ring_generic.h index ea7dbe5b9..3fd1150f6 100644 --- a/lib/librte_ring/rte_ring_generic.h +++ b/lib/librte_ring/rte_ring_generic.h @@ -1,6 +1,6 @@ /* SPDX-License-Identifier: BSD-3-Clause * - * Copyright (c) 2010-2017 Intel Corporation + * Copyright (c) 2010-2019 Intel Corporation * Copyright (c) 2007-2009 Kip Macy kmacy@freebsd.org * All rights reserved. * Derived from FreeBSD's bufring.h @@ -11,7 +11,7 @@ #define _RTE_RING_GENERIC_H_ static __rte_always_inline void -update_tail(struct rte_ring_headtail *ht, uint32_t old_val, uint32_t new_val, +update_tail(struct rte_ring_headtail *ht, uintptr_t old_val, uintptr_t new_val, uint32_t single, uint32_t enqueue) { if (enqueue) @@ -55,7 +55,7 @@ update_tail(struct rte_ring_headtail *ht, uint32_t old_val, uint32_t new_val, static __rte_always_inline unsigned int __rte_ring_move_prod_head(struct rte_ring *r, unsigned int is_sp, unsigned int n, enum rte_ring_queue_behavior behavior, - uint32_t *old_head, uint32_t *new_head, + uintptr_t *old_head, uintptr_t *new_head, uint32_t *free_entries) { const uint32_t capacity = r->capacity; @@ -93,7 +93,8 @@ __rte_ring_move_prod_head(struct rte_ring *r, unsigned int is_sp, if (is_sp) r->prod.head = *new_head, success = 1; else - success = rte_atomic32_cmpset(&r->prod.head, + /* Built-in used to handle variable-sized head index. */ + success = __sync_bool_compare_and_swap(&r->prod.head, *old_head, *new_head); } while (unlikely(success == 0)); return n; @@ -125,7 +126,7 @@ __rte_ring_move_prod_head(struct rte_ring *r, unsigned int is_sp, static __rte_always_inline unsigned int __rte_ring_move_cons_head(struct rte_ring *r, unsigned int is_sc, unsigned int n, enum rte_ring_queue_behavior behavior, - uint32_t *old_head, uint32_t *new_head, + uintptr_t *old_head, uintptr_t *new_head, uint32_t *entries) { unsigned int max = n; @@ -161,8 +162,9 @@ __rte_ring_move_cons_head(struct rte_ring *r, unsigned int is_sc, if (is_sc) r->cons.head = *new_head, success = 1; else - success = rte_atomic32_cmpset(&r->cons.head, *old_head, - *new_head); + /* Built-in used to handle variable-sized head index. */ + success = __sync_bool_compare_and_swap(&r->cons.head, + *old_head, *new_head); } while (unlikely(success == 0)); return n; } -- 2.13.6