From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cunming Liang Subject: [PATCH v4 16/17] ring: add sched_yield to avoid spin forever Date: Mon, 2 Feb 2015 10:02:38 +0800 Message-ID: <1422842559-13617-17-git-send-email-cunming.liang@intel.com> References: <1422491072-5114-1-git-send-email-cunming.liang@intel.com> <1422842559-13617-1-git-send-email-cunming.liang@intel.com> To: dev-VfR2kkLFssw@public.gmane.org Return-path: In-Reply-To: <1422842559-13617-1-git-send-email-cunming.liang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces-VfR2kkLFssw@public.gmane.org Sender: "dev" Add a sched_yield() syscall if the thread spins for too long, waiting other thread to finish its operations on the ring. That gives pre-empted thread a chance to proceed and finish with ring enqnue/dequeue operation. The purpose is to reduce contention on the ring. Signed-off-by: Cunming Liang --- lib/librte_ring/rte_ring.h | 35 +++++++++++++++++++++++++++++------ 1 file changed, 29 insertions(+), 6 deletions(-) diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h index 39bacdd..c402c73 100644 --- a/lib/librte_ring/rte_ring.h +++ b/lib/librte_ring/rte_ring.h @@ -126,6 +126,7 @@ struct rte_ring_debug_stats { #define RTE_RING_NAMESIZE 32 /**< The maximum length of a ring name. */ #define RTE_RING_MZ_PREFIX "RG_" +#define RTE_RING_PAUSE_REP 0x100 /**< yield after num of times pause. */ /** * An RTE ring structure. @@ -410,7 +411,7 @@ __rte_ring_mp_do_enqueue(struct rte_ring *r, void * const *obj_table, uint32_t cons_tail, free_entries; const unsigned max = n; int success; - unsigned i; + unsigned i, rep; uint32_t mask = r->prod.mask; int ret; @@ -468,8 +469,19 @@ __rte_ring_mp_do_enqueue(struct rte_ring *r, void * const *obj_table, * If there are other enqueues in progress that preceded us, * we need to wait for them to complete */ - while (unlikely(r->prod.tail != prod_head)) - rte_pause(); + do { + /* avoid spin too long waiting for other thread finish */ + for (rep = RTE_RING_PAUSE_REP; + rep != 0 && r->prod.tail != prod_head; rep--) + rte_pause(); + + /* + * It gives pre-empted thread a chance to proceed and + * finish with ring enqnue operation. + */ + if (rep == 0) + sched_yield(); + } while (rep == 0); r->prod.tail = prod_next; return ret; @@ -589,7 +601,7 @@ __rte_ring_mc_do_dequeue(struct rte_ring *r, void **obj_table, uint32_t cons_next, entries; const unsigned max = n; int success; - unsigned i; + unsigned i, rep; uint32_t mask = r->prod.mask; /* move cons.head atomically */ @@ -634,8 +646,19 @@ __rte_ring_mc_do_dequeue(struct rte_ring *r, void **obj_table, * If there are other dequeues in progress that preceded us, * we need to wait for them to complete */ - while (unlikely(r->cons.tail != cons_head)) - rte_pause(); + do { + /* avoid spin too long waiting for other thread finish */ + for (rep = RTE_RING_PAUSE_REP; + rep != 0 && r->cons.tail != cons_head; rep--) + rte_pause(); + + /* + * It gives pre-empted thread a chance to proceed and + * finish with ring denqnue operation. + */ + if (rep == 0) + sched_yield(); + } while (rep == 0); __RING_STAT_ADD(r, deq_success, n); r->cons.tail = cons_next; -- 1.8.1.4