X-Git-Url: https://gerrit.fd.io/r/gitweb?a=blobdiff_plain;f=src%2Fsvm%2Fsvm_fifo.h;h=42efb5af6b315e20043c9271b3f228525fdde649;hb=fb079585c;hp=80e5b0f2d39c23d3e07d46d44627ac82a534d1df;hpb=3e350af5d3e9744a4529a28dd293b2d4601442f7;p=vpp.git

diff --git a/src/svm/svm_fifo.h b/src/svm/svm_fifo.h
index 80e5b0f2d39..42efb5af6b3 100644
--- a/src/svm/svm_fifo.h
+++ b/src/svm/svm_fifo.h
@@ -1,5 +1,9 @@
 /*
- * Copyright (c) 2016 Cisco and/or its affiliates.
+ * Copyright (c) 2016-2019 Cisco and/or its affiliates.
+ * Copyright (c) 2019 Arm Limited
+ * Copyright (c) 2010-2017 Intel Corporation and/or its affiliates.
+ * Copyright (c) 2007-2009 Kip Macy kmacy@freebsd.org
+ * Inspired from DPDK rte_ring.h (SPSC only) (derived from freebsd bufring.h).
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
@@ -17,159 +21,850 @@
 
 #include <vppinfra/clib.h>
 #include <vppinfra/vec.h>
-#include <vppinfra/mheap.h>
-#include <vppinfra/heap.h>
 #include <vppinfra/pool.h>
 #include <vppinfra/format.h>
-#include <pthread.h>
+#include <svm/fifo_types.h>
+
+#define OOO_SEGMENT_INVALID_INDEX 	((u32)~0)
+#define SVM_FIFO_INVALID_SESSION_INDEX 	((u32)~0)
+#define SVM_FIFO_INVALID_INDEX		((u32)~0)
+
+typedef enum svm_fifo_deq_ntf_
+{
+  SVM_FIFO_NO_DEQ_NOTIF = 0,		/**< No notification requested */
+  SVM_FIFO_WANT_DEQ_NOTIF = 1,		/**< Notify on dequeue */
+  SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL = 2,	/**< Notify on transition from full */
+  SVM_FIFO_WANT_DEQ_NOTIF_IF_EMPTY = 4, /**< Notify on transition to empty */
+  SVM_FIFO_WANT_DEQ_NOTIF_IF_LEQ_THRESH = 5, /**< Notify on transition to less
+					       than or equal threshold */
+} svm_fifo_deq_ntf_t;
+
+typedef enum svm_fifo_flag_
+{
+  SVM_FIFO_F_LL_TRACKED = 1 << 0,
+} svm_fifo_flag_t;
 
 typedef enum
 {
-  SVM_FIFO_TAG_NOT_HELD = 0,
-  SVM_FIFO_TAG_DEQUEUE,
-  SVM_FIFO_TAG_ENQUEUE,
-} svm_lock_tag_t;
+  SVM_FIFO_EFULL = -2,
+  SVM_FIFO_EEMPTY = -3,
+  SVM_FIFO_EGROW = -4,
+} svm_fifo_err_t;
 
-/** Out-of-order segment */
-typedef struct
+typedef struct svm_fifo_seg_
 {
-  u32 next;	/**< Next linked-list element pool index */
-  u32 prev;	/**< Previous linked-list element pool index */
+  u8 *data;
+  u32 len;
+} svm_fifo_seg_t;
 
-  u32 fifo_position;	/**< Start of segment, normalized*/
-  u32 length;		/**< Length of segment */
-} ooo_segment_t;
+#if SVM_FIFO_TRACE
+#define svm_fifo_trace_add(_f, _s, _l, _t)		\
+{							\
+  svm_fifo_trace_elem_t *trace_elt;			\
+  vec_add2(_f->trace, trace_elt, 1);			\
+  trace_elt->offset = _s;				\
+  trace_elt->len = _l;					\
+  trace_elt->action = _t;				\
+}
+#else
+#define svm_fifo_trace_add(_f, _s, _l, _t)
+#endif
 
-#define OOO_SEGMENT_INVALID_INDEX ((u32)~0)
+u8 *svm_fifo_dump_trace (u8 * s, svm_fifo_t * f);
+u8 *svm_fifo_replay (u8 * s, svm_fifo_t * f, u8 no_read, u8 verbose);
 
-typedef struct
+/**
+ * Load head and tail optimized for consumer
+ *
+ * Internal function.
+ */
+static inline void
+f_load_head_tail_cons (svm_fifo_t * f, u32 * head, u32 * tail)
 {
-  volatile u32 cursize;		/**< current fifo size */
-  u32 nitems;
-    CLIB_CACHE_LINE_ALIGN_MARK (end_cursize);
+  /* load-relaxed: consumer owned index */
+  *head = f->shr->head;
+  /* load-acq: consumer foreign index (paired with store-rel in producer) */
+  *tail = clib_atomic_load_acq_n (&f->shr->tail);
+}
 
-  pthread_mutex_t mutex;	/* 8 bytes */
-  pthread_cond_t condvar;	/* 8 bytes */
-  svm_lock_tag_t tag;
+/** Load head and tail optimized for producer
+ *
+ * Internal function
+ */
+static inline void
+f_load_head_tail_prod (svm_fifo_t * f, u32 * head, u32 * tail)
+{
+  /* load relaxed: producer owned index */
+  *tail = f->shr->tail;
+  /* load-acq: producer foreign index (paired with store-rel in consumer) */
+  *head = clib_atomic_load_acq_n (&f->shr->head);
+}
 
-  volatile u8 has_event;	/**< non-zero if deq event exists */
-  u32 owner_pid;
+/**
+ * Load head and tail independent of producer/consumer role
+ *
+ * Internal function.
+ */
+static inline void
+f_load_head_tail_all_acq (svm_fifo_t * f, u32 * head, u32 * tail)
+{
+  /* load-acq : consumer foreign index (paired with store-rel) */
+  *tail = clib_atomic_load_acq_n (&f->shr->tail);
+  /* load-acq : producer foriegn index (paired with store-rel) */
+  *head = clib_atomic_load_acq_n (&f->shr->head);
+}
 
-  /* Backpointers */
-  u32 server_session_index;
-  u32 client_session_index;
-  u8 server_thread_index;
-  u8 client_thread_index;
-    CLIB_CACHE_LINE_ALIGN_MARK (end_shared);
-  u32 head;
-    CLIB_CACHE_LINE_ALIGN_MARK (end_consumer);
+/**
+ * Fifo current size, i.e., number of bytes enqueued
+ *
+ * Internal function.
+ */
+static inline u32
+f_cursize (svm_fifo_t * f, u32 head, u32 tail)
+{
+  return tail - head;
+}
 
-  /* producer */
-  u32 tail;
+/**
+ * Fifo free bytes, i.e., number of free bytes
+ *
+ * Internal function
+ */
+static inline u32
+f_free_count (svm_fifo_t * f, u32 head, u32 tail)
+{
+  return (f->shr->size - f_cursize (f, head, tail));
+}
 
-  ooo_segment_t *ooo_segments;	/**< Pool of ooo segments */
-  u32 ooos_list_head;		/**< Head of out-of-order linked-list */
-  u32 ooos_newest;		/**< Last segment to have been updated */
+always_inline u32
+f_chunk_end (svm_fifo_chunk_t * c)
+{
+  return c->start_byte + c->length;
+}
 
-    CLIB_CACHE_LINE_ALIGN_MARK (data);
-} svm_fifo_t;
+always_inline int
+f_pos_lt (u32 a, u32 b)
+{
+  return ((i32) (a - b) < 0);
+}
 
-static inline int
-svm_fifo_lock (svm_fifo_t * f, u32 pid, u32 tag, int nowait)
+always_inline int
+f_pos_leq (u32 a, u32 b)
 {
-  if (PREDICT_TRUE (nowait == 0))
-    pthread_mutex_lock (&f->mutex);
-  else
-    {
-      if (pthread_mutex_trylock (&f->mutex))
-	return -1;
-    }
-  f->owner_pid = pid;
-  f->tag = tag;
-  return 0;
+  return ((i32) (a - b) <= 0);
 }
 
-static inline void
-svm_fifo_unlock (svm_fifo_t * f)
+always_inline int
+f_pos_gt (u32 a, u32 b)
+{
+  return ((i32) (a - b) > 0);
+}
+
+always_inline int
+f_pos_geq (u32 a, u32 b)
+{
+  return ((i32) (a - b) >= 0);
+}
+
+always_inline u8
+f_chunk_includes_pos (svm_fifo_chunk_t * c, u32 pos)
+{
+  return (f_pos_geq (pos, c->start_byte)
+	  && f_pos_lt (pos, c->start_byte + c->length));
+}
+
+always_inline svm_fifo_chunk_t *
+f_start_cptr (svm_fifo_t *f)
+{
+  return fs_chunk_ptr (f->fs_hdr, f->shr->start_chunk);
+}
+
+always_inline svm_fifo_chunk_t *
+f_end_cptr (svm_fifo_t *f)
+{
+  return fs_chunk_ptr (f->fs_hdr, f->shr->end_chunk);
+}
+
+always_inline svm_fifo_chunk_t *
+f_head_cptr (svm_fifo_t *f)
+{
+  return fs_chunk_ptr (f->fs_hdr, f->shr->head_chunk);
+}
+
+always_inline svm_fifo_chunk_t *
+f_tail_cptr (svm_fifo_t *f)
+{
+  return fs_chunk_ptr (f->fs_hdr, f->shr->tail_chunk);
+}
+
+always_inline svm_fifo_chunk_t *
+f_cptr (svm_fifo_t *f, fs_sptr_t cp)
+{
+  return fs_chunk_ptr (f->fs_hdr, cp);
+}
+
+always_inline fs_sptr_t
+f_csptr (svm_fifo_t *f, svm_fifo_chunk_t *c)
+{
+  return fs_chunk_sptr (f->fs_hdr, c);
+}
+
+always_inline void
+f_csptr_link (svm_fifo_t *f, fs_sptr_t cp, svm_fifo_chunk_t *c)
+{
+  fs_chunk_ptr (f->fs_hdr, cp)->next = fs_chunk_sptr (f->fs_hdr, c);
+}
+
+/**
+ * Create fifo of requested size
+ *
+ * Allocates fifo on current heap.
+ *
+ * @param size		data size in bytes for fifo to be allocated. Will be
+ * 			rounded to the next highest power-of-two value.
+ * @return 		pointer to new fifo
+ */
+svm_fifo_t *svm_fifo_alloc (u32 size);
+/**
+ * Initialize fifo
+ *
+ * @param f		fifo
+ * @param size		size for fifo
+ */
+void svm_fifo_init (svm_fifo_t * f, u32 size);
+/**
+ * Allocate a fifo chunk on heap
+ *
+ * If the chunk is allocated on a fifo segment, this should be called
+ * with the segment's heap pushed.
+ *
+ * @param size	chunk size in bytes. Will be rounded to the next highest
+ * 		power-of-two
+ * @return	new chunk or 0 if alloc failed
+ */
+svm_fifo_chunk_t *svm_fifo_chunk_alloc (u32 size);
+/**
+ * Ensure the whole fifo size is writeable
+ *
+ * Allocates enough chunks to cover the whole fifo size.
+ *
+ * @param f	fifo
+ */
+int svm_fifo_fill_chunk_list (svm_fifo_t * f);
+/**
+ * Provision and return chunks for number of bytes requested
+ *
+ * Allocates enough chunks to cover the bytes requested and returns them
+ * in the fifo segment array. The number of bytes provisioned may be less
+ * than requested if not enough segments were provided.
+ *
+ * @param f		fifo
+ * @param fs		array of fifo segments
+ * @param n_segs	length of fifo segments array
+ * @param len		number of bytes to preallocate
+ * @return		number of fifo segments provisioned or error
+ */
+int svm_fifo_provision_chunks (svm_fifo_t *f, svm_fifo_seg_t *fs, u32 n_segs,
+			       u32 len);
+/**
+ * Initialize rbtrees used for ooo lookups
+ *
+ * @param f		fifo
+ * @param ooo_type	type of ooo operation (0 enqueue, 1 dequeue)
+ */
+void svm_fifo_init_ooo_lookup (svm_fifo_t * f, u8 ooo_type);
+/**
+ * Free fifo and associated state
+ *
+ * @param f	fifo
+ */
+void svm_fifo_free (svm_fifo_t * f);
+/**
+ * Cleanup fifo chunk lookup rb tree
+ *
+ * The rb tree is allocated in segment heap so this should be called
+ * with it pushed.
+ *
+ * @param f 	fifo to cleanup
+ */
+void svm_fifo_free_chunk_lookup (svm_fifo_t * f);
+/**
+ * Cleanup fifo ooo data
+ *
+ * The ooo data is allocated in producer process memory. The fifo
+ * segment heap should not be pushed.
+ *
+ * @param f	fifo to cleanup
+ */
+void svm_fifo_free_ooo_data (svm_fifo_t * f);
+/**
+ * Init fifo head and tail
+ *
+ * @param f	fifo
+ * @param head	head value that will be matched to a chunk
+ * @param tail	tail value that will be matched to a chunk
+ */
+void svm_fifo_init_pointers (svm_fifo_t * f, u32 head, u32 tail);
+/**
+ * Clone fifo
+ *
+ * Clones single/default chunk fifo. It does not work for fifos with
+ * multiple chunks.
+ */
+void svm_fifo_clone (svm_fifo_t * df, svm_fifo_t * sf);
+/**
+ * Enqueue data to fifo
+ *
+ * Data is enqueued and tail pointer is updated atomically. If the new data
+ * enqueued partly overlaps or "touches" an out-of-order segment, said segment
+ * is "consumed" and the number of bytes returned is appropriately updated.
+ *
+ * @param f	fifo
+ * @param len	length of data to copy
+ * @param src	buffer from where to copy the data
+ * @return	number of contiguous bytes that can be consumed or error
+ */
+int svm_fifo_enqueue (svm_fifo_t * f, u32 len, const u8 * src);
+/**
+ * Enqueue data to fifo with offset
+ *
+ * Data is enqueued without updating tail pointer. Instead, an out-of-order
+ * list of segments is generated and maintained. Fifo takes care of coalescing
+ * contiguous or overlapping segments.
+ *
+ * @param f		fifo
+ * @param offset	offset at which to copy the data
+ * @param len		len of data to copy
+ * @param src		buffer from where to copy the data
+ * @return		0 if enqueue was successful, error otherwise
+ */
+int svm_fifo_enqueue_with_offset (svm_fifo_t * f, u32 offset, u32 len,
+				  u8 * src);
+
+/**
+ * Advance tail pointer
+ *
+ * Useful for moving tail pointer after external enqueue.
+ *
+ * @param f		fifo
+ * @param len		number of bytes to add to tail
+ */
+void svm_fifo_enqueue_nocopy (svm_fifo_t * f, u32 len);
+/**
+ * Enqueue array of @ref svm_fifo_seg_t in order
+ *
+ * @param f		fifo
+ * @param segs		array of segments to enqueue
+ * @param n_segs	number of segments
+ * @param allow_partial	if set partial enqueues are allowed
+ * @return		len if enqueue was successful, error otherwise
+ */
+int svm_fifo_enqueue_segments (svm_fifo_t * f, const svm_fifo_seg_t segs[],
+			       u32 n_segs, u8 allow_partial);
+/**
+ * Overwrite fifo head with new data
+ *
+ * This should be typically used by dgram transport protocols that need
+ * to update the dgram header after dequeuing a chunk of data. It assumes
+ * that the dgram header is at most spread over two chunks.
+ *
+ * @param f		fifo
+ * @param src		src of new data
+ * @param len		length of new data
+ */
+void svm_fifo_overwrite_head (svm_fifo_t * f, u8 * src, u32 len);
+/**
+ * Dequeue data from fifo
+ *
+ * Data is dequeued to consumer provided buffer and head is atomically
+ * updated. This should not be used in combination with ooo lookups. If
+ * ooo peeking of data is needed in combination with dequeuing use @ref
+ * svm_fifo_dequeue_drop.
+ *
+ * @param f		fifo
+ * @param len		length of data to dequeue
+ * @param dst		buffer to where to dequeue the data
+ * @return		number of bytes dequeued or error
+ */
+int svm_fifo_dequeue (svm_fifo_t * f, u32 len, u8 * dst);
+/**
+ * Peek data from fifo
+ *
+ * Data is copied from requested offset into provided dst buffer. Head is
+ * not updated.
+ *
+ * @param f		fifo
+ * @param offset	offset from which to copy the data
+ * @param len		length of data to copy
+ * @param dst		buffer to where to dequeue the data
+ * @return		number of bytes peeked
+ */
+int svm_fifo_peek (svm_fifo_t * f, u32 offset, u32 len, u8 * dst);
+/**
+ * Dequeue and drop bytes from fifo
+ *
+ * Advances fifo head by requested amount of bytes.
+ *
+ * @param f		fifo
+ * @param len		number of bytes to drop
+ * @return		number of bytes dropped
+ */
+int svm_fifo_dequeue_drop (svm_fifo_t * f, u32 len);
+/**
+ * Dequeue and drop all bytes from fifo
+ *
+ * Advances head to tail position.
+ *
+ * @param f		fifo
+ */
+void svm_fifo_dequeue_drop_all (svm_fifo_t * f);
+/**
+ * Get pointers to fifo chunks data in @ref svm_fifo_seg_t array
+ *
+ * Populates fifo segment array with pointers to fifo chunk data and lengths.
+ * Because this returns pointers to data, it must be paired with
+ * @ref svm_fifo_dequeue_drop to actually release the fifo chunks after the
+ * data is consumed.
+ *
+ * @param f		fifo
+ * @param offset	offset from where to retrieve segments
+ * @param fs		array of fifo segments allocated by caller
+ * @param n_segs	number of fifo segments in array
+ * @param max_bytes	max bytes to be mapped to fifo segments
+ * @return 		number of bytes in fifo segments or SVM_FIFO_EEMPTY
+ */
+int svm_fifo_segments (svm_fifo_t * f, u32 offset, svm_fifo_seg_t * fs,
+		       u32 n_segs, u32 max_bytes);
+/**
+ * Add io events subscriber to list
+ *
+ * @param f	fifo
+ * @param sub	subscriber opaque index (typically app worker index)
+ */
+void svm_fifo_add_subscriber (svm_fifo_t * f, u8 sub);
+/**
+ * Remove io events subscriber form list
+ *
+ * @param f	fifo
+ * @param sub	subscriber index to be removed
+ */
+void svm_fifo_del_subscriber (svm_fifo_t * f, u8 subscriber);
+/**
+ * Number of out-of-order segments for fifo
+ *
+ * @param f	fifo
+ * @return	number of out of order segments
+ */
+u32 svm_fifo_n_ooo_segments (svm_fifo_t * f);
+/**
+ * First out-of-order segment for fifo
+ *
+ * @param f	fifo
+ * @return	first out-of-order segment for fifo
+ */
+ooo_segment_t *svm_fifo_first_ooo_segment (svm_fifo_t * f);
+/**
+ * Check if fifo is sane. Debug only.
+ *
+ * @param f	fifo
+ * @return 	1 if sane, 0 otherwise
+ */
+u8 svm_fifo_is_sane (svm_fifo_t * f);
+/**
+ * Number of chunks linked into the fifo
+ *
+ * @param f	fifo
+ * @return 	number of chunks in fifo linked list
+ */
+u32 svm_fifo_n_chunks (svm_fifo_t * f);
+format_function_t format_svm_fifo;
+
+/**
+ * Fifo max bytes to dequeue optimized for consumer
+ *
+ * @param f	fifo
+ * @return	max number of bytes that can be dequeued
+ */
+static inline u32
+svm_fifo_max_dequeue_cons (svm_fifo_t * f)
+{
+  u32 tail, head;
+  f_load_head_tail_cons (f, &head, &tail);
+  return f_cursize (f, head, tail);
+}
+
+/**
+ * Fifo max bytes to dequeue optimized for producer
+ *
+ * @param f	fifo
+ * @return	max number of bytes that can be dequeued
+ */
+static inline u32
+svm_fifo_max_dequeue_prod (svm_fifo_t * f)
 {
-  f->owner_pid = 0;
-  f->tag = 0;
-  CLIB_MEMORY_BARRIER ();
-  pthread_mutex_unlock (&f->mutex);
+  u32 tail, head;
+  f_load_head_tail_prod (f, &head, &tail);
+  return f_cursize (f, head, tail);
 }
 
+/**
+ * Fifo max bytes to dequeue
+ *
+ * Note: use producer or consumer specific functions for performance:
+ * @ref svm_fifo_max_dequeue_cons (svm_fifo_t *f)
+ * @ref svm_fifo_max_dequeue_prod (svm_fifo_t *f)
+ */
 static inline u32
 svm_fifo_max_dequeue (svm_fifo_t * f)
 {
-  return f->cursize;
+  u32 tail, head;
+  f_load_head_tail_all_acq (f, &head, &tail);
+  return f_cursize (f, head, tail);
+}
+
+/**
+ * Check if fifo is full optimized for producer
+ *
+ * @param f	fifo
+ * @return	1 if fifo is full 0 otherwise
+ */
+static inline int
+svm_fifo_is_full_prod (svm_fifo_t * f)
+{
+  return (svm_fifo_max_dequeue_prod (f) == f->shr->size);
+}
+
+/* Check if fifo is full.
+ *
+ * Note: use producer or consumer specific functions for performance.
+ * @ref svm_fifo_is_full_prod (svm_fifo_t * f)
+ * add cons version if needed
+ */
+static inline int
+svm_fifo_is_full (svm_fifo_t * f)
+{
+  return (svm_fifo_max_dequeue (f) == f->shr->size);
+}
+
+/**
+ * Check if fifo is empty optimized for consumer
+ *
+ * @param f 	fifo
+ * @return	1 if fifo is empty 0 otherwise
+ */
+static inline int
+svm_fifo_is_empty_cons (svm_fifo_t * f)
+{
+  return (svm_fifo_max_dequeue_cons (f) == 0);
+}
+
+/**
+ * Check if fifo is empty optimized for producer
+ *
+ * @param f	fifo
+ * @return	1 if fifo is empty 0 otherwise
+ */
+static inline int
+svm_fifo_is_empty_prod (svm_fifo_t * f)
+{
+  return (svm_fifo_max_dequeue_prod (f) == 0);
+}
+
+/**
+ * Check if fifo is empty
+ *
+ * Note: use producer or consumer specific functions for perfomance.
+ * @ref svm_fifo_is_empty_cons (svm_fifo_t * f)
+ * @ref svm_fifo_is_empty_prod (svm_fifo_t * f)
+ */
+static inline int
+svm_fifo_is_empty (svm_fifo_t * f)
+{
+  return (svm_fifo_max_dequeue (f) == 0);
+}
+
+/**
+ * Check if fifo is wrapped
+ *
+ * @param f	fifo
+ * @return 	1 if 'normalized' head is ahead of tail
+ */
+static inline u8
+svm_fifo_is_wrapped (svm_fifo_t * f)
+{
+  u32 head, tail;
+  f_load_head_tail_all_acq (f, &head, &tail);
+  return head > tail;
 }
 
+/**
+ * Maximum number of bytes that can be enqueued into fifo
+ *
+ * Optimized for producer
+ *
+ * @param f	fifo
+ * @return	max number of bytes that can be enqueued into fifo
+ */
+static inline u32
+svm_fifo_max_enqueue_prod (svm_fifo_t * f)
+{
+  u32 head, tail;
+  f_load_head_tail_prod (f, &head, &tail);
+  return f_free_count (f, head, tail);
+}
+
+/* Maximum number of bytes that can be enqueued into fifo
+ *
+ * Note: use producer or consumer specific functions for performance.
+ * @ref svm_fifo_max_enqueue_prod (svm_fifo_t *f)
+ * add consumer specific version if needed.
+ */
 static inline u32
 svm_fifo_max_enqueue (svm_fifo_t * f)
 {
-  return f->nitems - svm_fifo_max_dequeue (f);
+  u32 head, tail;
+  f_load_head_tail_all_acq (f, &head, &tail);
+  return f_free_count (f, head, tail);
 }
 
+/**
+ * Max contiguous chunk of data that can be read.
+ *
+ * Should only be called by consumers.
+ */
+u32 svm_fifo_max_read_chunk (svm_fifo_t * f);
+
+/**
+ * Max contiguous chunk of data that can be written
+ *
+ * Should only be called by producers
+ */
+u32 svm_fifo_max_write_chunk (svm_fifo_t * f);
+
+/**
+ * Fifo number of subscribers getter
+ *
+ * @param f	fifo
+ * @return	number of subscribers
+ */
+static inline u8
+svm_fifo_n_subscribers (svm_fifo_t * f)
+{
+  return f->shr->n_subscribers;
+}
+
+/**
+ * Check if fifo has out-of-order data
+ *
+ * @param f	fifo
+ * @return	1 if fifo has ooo data, 0 otherwise
+ */
 static inline u8
 svm_fifo_has_ooo_data (svm_fifo_t * f)
 {
   return f->ooos_list_head != OOO_SEGMENT_INVALID_INDEX;
 }
 
+static inline ooo_segment_t *
+svm_fifo_newest_ooo_segment (svm_fifo_t * f)
+{
+  if (f->ooos_newest == OOO_SEGMENT_INVALID_INDEX)
+    return 0;
+  return pool_elt_at_index (f->ooo_segments, f->ooos_newest);
+}
+
+static inline void
+svm_fifo_newest_ooo_segment_reset (svm_fifo_t * f)
+{
+  f->ooos_newest = OOO_SEGMENT_INVALID_INDEX;
+}
+
+static inline u32
+ooo_segment_offset_prod (svm_fifo_t * f, ooo_segment_t * s)
+{
+  u32 tail;
+  /* load-relaxed: producer owned index */
+  tail = f->shr->tail;
+
+  return (s->start - tail);
+}
+
+static inline u32
+ooo_segment_length (svm_fifo_t * f, ooo_segment_t * s)
+{
+  return s->length;
+}
+
+static inline u32
+svm_fifo_size (svm_fifo_t * f)
+{
+  return f->shr->size;
+}
+
+static inline void
+svm_fifo_set_size (svm_fifo_t * f, u32 size)
+{
+  if (size > (1 << f->fs_hdr->max_log2_fifo_size))
+    return;
+  fsh_virtual_mem_update (f->fs_hdr, f->shr->slice_index,
+			  (int) f->shr->size - size);
+  f->shr->size = size;
+}
+
 /**
- * Sets fifo event flag.
+ * Check if fifo has io event
  *
- * @return 1 if flag was not set.
+ * @param f	fifo
+ * @return	1 if fifo has event, 0 otherwise
+ */
+static inline int
+svm_fifo_has_event (svm_fifo_t * f)
+{
+  return f->shr->has_event;
+}
+
+/**
+ * Set fifo event flag.
+ *
+ * Forces release semantics.
+ *
+ * @param f	fifo
+ * @return 	1 if flag was not set, 0 otherwise
  */
 always_inline u8
 svm_fifo_set_event (svm_fifo_t * f)
 {
-  /* Probably doesn't need to be atomic. Still, better avoid surprises */
-  return __sync_lock_test_and_set (&f->has_event, 1) == 0;
+  return !clib_atomic_swap_rel_n (&f->shr->has_event, 1);
 }
 
 /**
- * Unsets fifo event flag.
+ * Unset fifo event flag.
+ *
+ * Forces acquire semantics
+ *
+ * @param f	fifo
  */
 always_inline void
 svm_fifo_unset_event (svm_fifo_t * f)
 {
-  /* Probably doesn't need to be atomic. Still, better avoid surprises */
-  __sync_lock_test_and_set (&f->has_event, 0);
+  clib_atomic_swap_acq_n (&f->shr->has_event, 0);
 }
 
-svm_fifo_t *svm_fifo_create (u32 data_size_in_bytes);
-
-int svm_fifo_enqueue_nowait (svm_fifo_t * f, int pid, u32 max_bytes,
-			     u8 * copy_from_here);
-
-int svm_fifo_enqueue_with_offset (svm_fifo_t * f, int pid,
-				  u32 offset, u32 required_bytes,
-				  u8 * copy_from_here);
+/**
+ * Set specific want notification flag
+ *
+ * For list of flags see @ref svm_fifo_deq_ntf_t
+ *
+ * @param f		fifo
+ * @param ntf_type	type of notification requested
+ */
+static inline void
+svm_fifo_add_want_deq_ntf (svm_fifo_t * f, u8 ntf_type)
+{
+  f->shr->want_deq_ntf |= ntf_type;
+}
 
-int svm_fifo_dequeue_nowait (svm_fifo_t * f, int pid, u32 max_bytes,
-			     u8 * copy_here);
+/**
+ * Clear specific want notification flag
+ *
+ * For list of flags see @ref svm_fifo_ntf_t
+ *
+ * @param f 		fifo
+ * @param ntf_type	type of notification to be cleared
+ */
+static inline void
+svm_fifo_del_want_deq_ntf (svm_fifo_t * f, u8 ntf_type)
+{
+  f->shr->want_deq_ntf &= ~ntf_type;
+}
 
-int svm_fifo_peek (svm_fifo_t * f, int pid, u32 offset, u32 max_bytes,
-		   u8 * copy_here);
-int svm_fifo_dequeue_drop (svm_fifo_t * f, int pid, u32 max_bytes);
+/**
+ * Clear the want notification flag and set has notification
+ *
+ * Should be used after enqueuing an event. This clears the
+ * SVM_FIFO_WANT_NOTIF flag but it does not clear
+ * SVM_FIFO_WANT_NOTIF_IF_FULL. If the latter was set, has_ntf is
+ * set to avoid enqueueing events for for all dequeue operations until
+ * it is manually cleared.
+ *
+ * @param f	fifo
+ */
+static inline void
+svm_fifo_clear_deq_ntf (svm_fifo_t * f)
+{
+  /* Set the flag if want_notif_if_full was the only ntf requested */
+  f->shr->has_deq_ntf =
+    f->shr->want_deq_ntf == SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL;
+  svm_fifo_del_want_deq_ntf (f, SVM_FIFO_WANT_DEQ_NOTIF |
+				  SVM_FIFO_WANT_DEQ_NOTIF_IF_LEQ_THRESH);
+}
 
-always_inline ooo_segment_t *
-svm_fifo_newest_ooo_segment (svm_fifo_t * f)
+/**
+ * Clear has notification flag
+ *
+ * The fifo generates only one event per SVM_FIFO_WANT_NOTIF_IF_FULL
+ * request and sets has_ntf. To received new events the flag must be
+ * cleared using this function.
+ *
+ * @param f	fifo
+ */
+static inline void
+svm_fifo_reset_has_deq_ntf (svm_fifo_t * f)
 {
-  return f->ooo_segments + f->ooos_newest;
+  f->shr->has_deq_ntf = 0;
 }
 
-always_inline u32
-ooo_segment_offset (svm_fifo_t * f, ooo_segment_t * s)
+/**
+ * Check if fifo needs dequeue notification
+ *
+ * Determines based on notification request flags and state of the fifo if
+ * an event should be generated.
+ *
+ * @param f		fifo
+ * @param n_last_deq	number of bytes last dequeued
+ * @return		1 if event should be generated, 0 otherwise
+ */
+static inline u8
+svm_fifo_needs_deq_ntf (svm_fifo_t * f, u32 n_last_deq)
 {
-  return ((f->nitems + s->fifo_position - f->tail) % f->nitems);
+  u8 want_ntf = f->shr->want_deq_ntf;
+
+  if (PREDICT_TRUE (want_ntf == SVM_FIFO_NO_DEQ_NOTIF))
+    return 0;
+  else if (want_ntf & SVM_FIFO_WANT_DEQ_NOTIF)
+    return 1;
+  if (want_ntf & SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL)
+    {
+      u32 max_deq = svm_fifo_max_dequeue_cons (f);
+      u32 size = f->shr->size;
+      if (!f->shr->has_deq_ntf && max_deq < size &&
+	  max_deq + n_last_deq >= size)
+	return 1;
+    }
+  if (want_ntf & SVM_FIFO_WANT_DEQ_NOTIF_IF_EMPTY)
+    {
+      if (!f->shr->has_deq_ntf && svm_fifo_is_empty (f))
+	return 1;
+    }
+  if (want_ntf & SVM_FIFO_WANT_DEQ_NOTIF_IF_LEQ_THRESH)
+    {
+      if (!f->shr->has_deq_ntf &&
+	  (svm_fifo_max_dequeue (f) <= f->shr->deq_thresh))
+	return 1;
+    }
+  return 0;
 }
 
-always_inline u32
-ooo_segment_end_offset (svm_fifo_t * f, ooo_segment_t * s)
+/**
+ * Set the fifo dequeue threshold which will be used for notifications.
+ *
+ * Note: If not set, by default threshold is zero, equivalent to
+ * empty.
+ */
+static inline void
+svm_fifo_set_deq_thresh (svm_fifo_t *f, u32 thresh)
 {
-  return ((f->nitems + s->fifo_position + s->length - f->tail) % f->nitems);
+  f->shr->deq_thresh = thresh;
 }
 
 #endif /* __included_ssvm_fifo_h__ */