/* SPDX-License-Identifier: BSD-3-Clause
- * Copyright (c) 2018 Arm Limited
+ * Copyright (c) 2018-2020 Arm Limited
*/
#ifndef _RTE_RCU_QSBR_H_
/**
* @file
- * RTE Quiescent State Based Reclamation (QSBR)
+ *
+ * RTE Quiescent State Based Reclamation (QSBR).
+ *
+ * @warning
+ * @b EXPERIMENTAL:
+ * All functions in this file may be changed or removed without prior notice.
*
* Quiescent State (QS) is any point in the thread execution
* where the thread does not hold a reference to a data structure
#include <rte_lcore.h>
#include <rte_debug.h>
#include <rte_atomic.h>
+#include <rte_ring.h>
extern int rte_rcu_log_type;
#define __RTE_QSBR_CNT_THR_OFFLINE 0
#define __RTE_QSBR_CNT_INIT 1
+#define __RTE_QSBR_CNT_MAX ((uint64_t)~0)
+#define __RTE_QSBR_TOKEN_SIZE sizeof(uint64_t)
/* RTE Quiescent State variable structure.
* This structure has two elements that vary in size based on the
struct rte_rcu_qsbr {
uint64_t token __rte_cache_aligned;
/**< Counter to allow for multiple concurrent quiescent state queries */
+ uint64_t acked_token;
+ /**< Least token acked by all the threads in the last call to
+ * rte_rcu_qsbr_check API.
+ */
uint32_t num_elems __rte_cache_aligned;
/**< Number of elements in the thread ID array */
*/
} __rte_cache_aligned;
+/**
+ * Call back function called to free the resources.
+ *
+ * @param p
+ * Pointer provided while creating the defer queue
+ * @param e
+ * Pointer to the resource data stored on the defer queue
+ * @param n
+ * Number of resources to free. Currently, this is set to 1.
+ *
+ * @return
+ * None
+ */
+typedef void (*rte_rcu_qsbr_free_resource_t)(void *p, void *e, unsigned int n);
+
+#define RTE_RCU_QSBR_DQ_NAMESIZE RTE_RING_NAMESIZE
+
+/**
+ * Various flags supported.
+ */
+/**< Enqueue and reclaim operations are multi-thread safe by default.
+ * The call back functions registered to free the resources are
+ * assumed to be multi-thread safe.
+ * Set this flag if multi-thread safety is not required.
+ */
+#define RTE_RCU_QSBR_DQ_MT_UNSAFE 1
+
+/**
+ * Parameters used when creating the defer queue.
+ */
+struct rte_rcu_qsbr_dq_parameters {
+ const char *name;
+ /**< Name of the queue. */
+ uint32_t flags;
+ /**< Flags to control API behaviors */
+ uint32_t size;
+ /**< Number of entries in queue. Typically, this will be
+ * the same as the maximum number of entries supported in the
+ * lock free data structure.
+ * Data structures with unbounded number of entries is not
+ * supported currently.
+ */
+ uint32_t esize;
+ /**< Size (in bytes) of each element in the defer queue.
+ * This has to be multiple of 4B.
+ */
+ uint32_t trigger_reclaim_limit;
+ /**< Trigger automatic reclamation after the defer queue
+ * has at least these many resources waiting. This auto
+ * reclamation is triggered in rte_rcu_qsbr_dq_enqueue API
+ * call.
+ * If this is greater than 'size', auto reclamation is
+ * not triggered.
+ * If this is set to 0, auto reclamation is triggered
+ * in every call to rte_rcu_qsbr_dq_enqueue API.
+ */
+ uint32_t max_reclaim_size;
+ /**< When automatic reclamation is enabled, reclaim at the max
+ * these many resources. This should contain a valid value, if
+ * auto reclamation is on. Setting this to 'size' or greater will
+ * reclaim all possible resources currently on the defer queue.
+ */
+ rte_rcu_qsbr_free_resource_t free_fn;
+ /**< Function to call to free the resource. */
+ void *p;
+ /**< Pointer passed to the free function. Typically, this is the
+ * pointer to the data structure to which the resource to free
+ * belongs. This can be NULL.
+ */
+ struct rte_rcu_qsbr *v;
+ /**< RCU QSBR variable to use for this defer queue */
+};
+
+/* RTE defer queue structure.
+ * This structure holds the defer queue. The defer queue is used to
+ * hold the deleted entries from the data structure that are not
+ * yet freed.
+ */
+struct rte_rcu_qsbr_dq;
+
/**
* @warning
* @b EXPERIMENTAL: this API may change without prior notice
* call this API before calling rte_rcu_qsbr_quiescent. This can be called
* during initialization or as part of the packet processing loop.
*
- * The reader thread must call rte_rcu_thread_offline API, before
+ * The reader thread must call rte_rcu_qsbr_thread_offline API, before
* calling any functions that block, to ensure that rte_rcu_qsbr_check
* API does not wait indefinitely for the reader thread to update its QS.
*
* This can be called during initialization or as part of the packet
* processing loop.
*
- * The reader thread must call rte_rcu_thread_offline API, before
+ * The reader thread must call rte_rcu_qsbr_thread_offline API, before
* calling any functions that block, to ensure that rte_rcu_qsbr_check
* API does not wait indefinitely for the reader thread to update its QS.
*
*/
t = __atomic_load_n(&v->token, __ATOMIC_ACQUIRE);
- /* Inform the writer that updates are visible to this reader.
+ /* Check if there are updates available from the writer.
+ * Inform the writer that updates are visible to this reader.
* Prior loads of the shared data structure should not move
* beyond this store. Hence use store-release.
*/
- __atomic_store_n(&v->qsbr_cnt[thread_id].cnt,
- t, __ATOMIC_RELEASE);
+ if (t != __atomic_load_n(&v->qsbr_cnt[thread_id].cnt, __ATOMIC_RELAXED))
+ __atomic_store_n(&v->qsbr_cnt[thread_id].cnt,
+ t, __ATOMIC_RELEASE);
__RTE_RCU_DP_LOG(DEBUG, "%s: update: token = %"PRIu64", Thread ID = %d",
__func__, t, thread_id);
uint64_t bmap;
uint64_t c;
uint64_t *reg_thread_id;
+ uint64_t acked_token = __RTE_QSBR_CNT_MAX;
for (i = 0, reg_thread_id = __RTE_QSBR_THRID_ARRAY_ELM(v, 0);
i < v->num_elems;
__RTE_RCU_DP_LOG(DEBUG,
"%s: status: token = %"PRIu64", wait = %d, Thread QS cnt = %"PRIu64", Thread ID = %d",
__func__, t, wait, c, id+j);
+
/* Counter is not checked for wrap-around condition
* as it is a 64b counter.
*/
continue;
}
+ /* This thread is in quiescent state. Use the counter
+ * to find the least acknowledged token among all the
+ * readers.
+ */
+ if (c != __RTE_QSBR_CNT_THR_OFFLINE && acked_token > c)
+ acked_token = c;
+
bmap &= ~(1UL << j);
}
}
+ /* All readers are checked, update least acknowledged token.
+ * There might be multiple writers trying to update this. There is
+ * no need to update this very accurately using compare-and-swap.
+ */
+ if (acked_token != __RTE_QSBR_CNT_MAX)
+ __atomic_store_n(&v->acked_token, acked_token,
+ __ATOMIC_RELAXED);
+
return 1;
}
uint32_t i;
struct rte_rcu_qsbr_cnt *cnt;
uint64_t c;
+ uint64_t acked_token = __RTE_QSBR_CNT_MAX;
for (i = 0, cnt = v->qsbr_cnt; i < v->max_threads; i++, cnt++) {
__RTE_RCU_DP_LOG(DEBUG,
__RTE_RCU_DP_LOG(DEBUG,
"%s: status: token = %"PRIu64", wait = %d, Thread QS cnt = %"PRIu64", Thread ID = %d",
__func__, t, wait, c, i);
+
/* Counter is not checked for wrap-around condition
* as it is a 64b counter.
*/
rte_pause();
}
+
+ /* This thread is in quiescent state. Use the counter to find
+ * the least acknowledged token among all the readers.
+ */
+ if (likely(c != __RTE_QSBR_CNT_THR_OFFLINE && acked_token > c))
+ acked_token = c;
}
+ /* All readers are checked, update least acknowledged token.
+ * There might be multiple writers trying to update this. There is
+ * no need to update this very accurately using compare-and-swap.
+ */
+ if (acked_token != __RTE_QSBR_CNT_MAX)
+ __atomic_store_n(&v->acked_token, acked_token,
+ __ATOMIC_RELAXED);
+
return 1;
}
{
RTE_ASSERT(v != NULL);
+ /* Check if all the readers have already acknowledged this token */
+ if (likely(t <= v->acked_token)) {
+ __RTE_RCU_DP_LOG(DEBUG,
+ "%s: check: token = %"PRIu64", wait = %d",
+ __func__, t, wait);
+ __RTE_RCU_DP_LOG(DEBUG,
+ "%s: status: least acked token = %"PRIu64"",
+ __func__, v->acked_token);
+ return 1;
+ }
+
if (likely(v->num_threads == v->max_threads))
return __rte_rcu_qsbr_check_all(v, t, wait);
else
int
rte_rcu_qsbr_dump(FILE *f, struct rte_rcu_qsbr *v);
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice
+ *
+ * Create a queue used to store the data structure elements that can
+ * be freed later. This queue is referred to as 'defer queue'.
+ *
+ * @param params
+ * Parameters to create a defer queue.
+ * @return
+ * On success - Valid pointer to defer queue
+ * On error - NULL
+ * Possible rte_errno codes are:
+ * - EINVAL - NULL parameters are passed
+ * - ENOMEM - Not enough memory
+ */
+__rte_experimental
+struct rte_rcu_qsbr_dq *
+rte_rcu_qsbr_dq_create(const struct rte_rcu_qsbr_dq_parameters *params);
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice
+ *
+ * Enqueue one resource to the defer queue and start the grace period.
+ * The resource will be freed later after at least one grace period
+ * is over.
+ *
+ * If the defer queue is full, it will attempt to reclaim resources.
+ * It will also reclaim resources at regular intervals to avoid
+ * the defer queue from growing too big.
+ *
+ * Multi-thread safety is provided as the defer queue configuration.
+ * When multi-thread safety is requested, it is possible that the
+ * resources are not stored in their order of deletion. This results
+ * in resources being held in the defer queue longer than they should.
+ *
+ * @param dq
+ * Defer queue to allocate an entry from.
+ * @param e
+ * Pointer to resource data to copy to the defer queue. The size of
+ * the data to copy is equal to the element size provided when the
+ * defer queue was created.
+ * @return
+ * On success - 0
+ * On error - 1 with rte_errno set to
+ * - EINVAL - NULL parameters are passed
+ * - ENOSPC - Defer queue is full. This condition can not happen
+ * if the defer queue size is equal (or larger) than the
+ * number of elements in the data structure.
+ */
+__rte_experimental
+int
+rte_rcu_qsbr_dq_enqueue(struct rte_rcu_qsbr_dq *dq, void *e);
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice
+ *
+ * Free resources from the defer queue.
+ *
+ * This API is multi-thread safe.
+ *
+ * @param dq
+ * Defer queue to free an entry from.
+ * @param n
+ * Maximum number of resources to free.
+ * @param freed
+ * Number of resources that were freed.
+ * @param pending
+ * Number of resources pending on the defer queue. This number might not
+ * be accurate if multi-thread safety is configured.
+ * @param available
+ * Number of resources that can be added to the defer queue.
+ * This number might not be accurate if multi-thread safety is configured.
+ * @return
+ * On successful reclamation of at least 1 resource - 0
+ * On error - 1 with rte_errno set to
+ * - EINVAL - NULL parameters are passed
+ */
+__rte_experimental
+int
+rte_rcu_qsbr_dq_reclaim(struct rte_rcu_qsbr_dq *dq, unsigned int n,
+ unsigned int *freed, unsigned int *pending, unsigned int *available);
+
+/**
+ * @warning
+ * @b EXPERIMENTAL: this API may change without prior notice
+ *
+ * Delete a defer queue.
+ *
+ * It tries to reclaim all the resources on the defer queue.
+ * If any of the resources have not completed the grace period
+ * the reclamation stops and returns immediately. The rest of
+ * the resources are not reclaimed and the defer queue is not
+ * freed.
+ *
+ * @param dq
+ * Defer queue to delete.
+ * @return
+ * On success - 0
+ * On error - 1
+ * Possible rte_errno codes are:
+ * - EAGAIN - Some of the resources have not completed at least 1 grace
+ * period, try again.
+ */
+__rte_experimental
+int
+rte_rcu_qsbr_dq_delete(struct rte_rcu_qsbr_dq *dq);
+
#ifdef __cplusplus
}
#endif
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