X-Git-Url: https://gerrit.fd.io/r/gitweb?a=blobdiff_plain;f=src%2Fsvm%2Fsvm_fifo.h;h=b5b26ac479b369db50533184fc3b0d1788013440;hb=cefd5d8806b9db7210192f53fdc2b8a60d4dc271;hp=d7852a79b32aea3c7bb23b05aa34a578a14f8ee2;hpb=326b81e30e63a8296df51d85e6514356cd737225;p=vpp.git

diff --git a/src/svm/svm_fifo.h b/src/svm/svm_fifo.h
index d7852a79b32..b5b26ac479b 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:
@@ -17,28 +21,31 @@
 
 #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 <vppinfra/rbtree.h>
 
 /** Out-of-order segment */
 typedef struct
 {
   u32 next;	/**< Next linked-list element pool index */
   u32 prev;	/**< Previous linked-list element pool index */
-
   u32 start;	/**< Start of segment, normalized*/
   u32 length;	/**< Length of segment */
 } ooo_segment_t;
 
-format_function_t format_ooo_segment;
-format_function_t format_ooo_list;
-
 #define SVM_FIFO_TRACE 			(0)
 #define OOO_SEGMENT_INVALID_INDEX 	((u32)~0)
 #define SVM_FIFO_INVALID_SESSION_INDEX 	((u32)~0)
+#define SVM_FIFO_INVALID_INDEX		((u32)~0)
+#define SVM_FIFO_MAX_EVT_SUBSCRIBERS	7
+
+typedef enum svm_fifo_tx_ntf_
+{
+  SVM_FIFO_NO_TX_NOTIF = 0,
+  SVM_FIFO_WANT_TX_NOTIF = 1,
+  SVM_FIFO_WANT_TX_NOTIF_IF_FULL = 2,
+} svm_fifo_tx_ntf_t;
 
 typedef struct
 {
@@ -47,52 +54,81 @@ typedef struct
   u32 action;
 } svm_fifo_trace_elem_t;
 
-typedef struct _svm_fifo
+typedef struct svm_fifo_chunk_
 {
-  volatile u32 cursize;		/**< current fifo size */
-  u32 nitems;
-    CLIB_CACHE_LINE_ALIGN_MARK (end_cursize);
+  u32 start_byte;		/**< chunk start byte */
+  u32 length;			/**< length of chunk in bytes */
+  struct svm_fifo_chunk_ *next;	/**< pointer to next chunk in linked-lists */
+  u8 data[0];			/**< start of chunk data */
+} svm_fifo_chunk_t;
 
+typedef enum svm_fifo_flag_
+{
+  SVM_FIFO_F_MULTI_CHUNK = 1 << 0,
+  SVM_FIFO_F_GROW = 1 << 1,
+  SVM_FIFO_F_SHRINK = 1 << 2,
+  SVM_FIFO_F_COLLECT_CHUNKS = 1 << 3,
+  SVM_FIFO_F_LL_TRACKED = 1 << 4,
+} svm_fifo_flag_t;
+
+typedef struct _svm_fifo
+{
+  CLIB_CACHE_LINE_ALIGN_MARK (shared_first);
+  u32 size;			/**< size of the fifo in bytes */
+  u32 nitems;			/**< usable size (size-1) */
+  u8 flags;			/**< fifo flags */
+  svm_fifo_chunk_t *start_chunk;/**< first chunk in fifo chunk list */
+  svm_fifo_chunk_t *end_chunk;	/**< end chunk in fifo chunk list */
+  svm_fifo_chunk_t *new_chunks;	/**< chunks yet to be added to list */
+  rb_tree_t chunk_lookup;
+
+    CLIB_CACHE_LINE_ALIGN_MARK (shared_second);
   volatile u32 has_event;	/**< non-zero if deq event exists */
+  u32 master_session_index;	/**< session layer session index */
+  u32 client_session_index;	/**< app session index */
+  u8 master_thread_index;	/**< session layer thread index */
+  u8 client_thread_index;	/**< app worker index */
+  i8 refcnt;			/**< reference count  */
+  u32 segment_manager;		/**< session layer segment manager index */
+  u32 segment_index;		/**< segment index in segment manager */
+  struct _svm_fifo *next;	/**< next in freelist/active chain */
+  struct _svm_fifo *prev;	/**< prev in active chain */
+  u32 size_decrement;		/**< bytes to remove from fifo */
 
-  /* Backpointers */
-  u32 master_session_index;
-  u32 client_session_index;
-  u8 master_thread_index;
-  u8 client_thread_index;
-  u32 segment_manager;
-  u32 ct_session_index;		/**< Local session index for vpp */
-    CLIB_CACHE_LINE_ALIGN_MARK (end_shared);
-  u32 head;
-  volatile u32 want_tx_evt;	/**< producer wants nudge */
-    CLIB_CACHE_LINE_ALIGN_MARK (end_consumer);
-
-  /* producer */
-  u32 tail;
+    CLIB_CACHE_LINE_ALIGN_MARK (consumer);
+  u32 head;			/**< fifo head position/byte */
+  svm_fifo_chunk_t *head_chunk;	/**< tracks chunk where head lands */
+  svm_fifo_chunk_t *ooo_deq;	/**< last chunk used for ooo dequeue */
+  volatile u32 want_tx_ntf;	/**< producer wants nudge */
+  volatile u32 has_tx_ntf;
 
-  ooo_segment_t *ooo_segments;	/**< Pool of ooo segments */
+    CLIB_CACHE_LINE_ALIGN_MARK (producer);
+  u32 tail;			/**< fifo tail position/byte */
   u32 ooos_list_head;		/**< Head of out-of-order linked-list */
+  svm_fifo_chunk_t *tail_chunk;	/**< tracks chunk where tail lands */
+  svm_fifo_chunk_t *ooo_enq;	/**< last chunk used for ooo enqueue */
+  ooo_segment_t *ooo_segments;	/**< Pool of ooo segments */
   u32 ooos_newest;		/**< Last segment to have been updated */
-  struct _svm_fifo *next;	/**< next in freelist/active chain */
-  struct _svm_fifo *prev;	/**< prev in active chain */
+  volatile u8 n_subscribers;	/**< Number of subscribers for io events */
+  u8 subscribers[SVM_FIFO_MAX_EVT_SUBSCRIBERS];
+
 #if SVM_FIFO_TRACE
   svm_fifo_trace_elem_t *trace;
 #endif
-  u32 freelist_index;		/**< aka log2(allocated_size) - const. */
-  i8 refcnt;			/**< reference count  */
-    CLIB_CACHE_LINE_ALIGN_MARK (data);
+
 } svm_fifo_t;
 
 typedef enum
 {
-  SVM_FIFO_FULL = -2,
+  SVM_FIFO_EFULL = -2,
+  SVM_FIFO_EEMPTY = -3,
 } svm_fifo_err_t;
 
-typedef struct svm_fifo_segment_
+typedef struct svm_fifo_seg_
 {
   u8 *data;
   u32 len;
-} svm_fifo_segment_t;
+} svm_fifo_seg_t;
 
 #if SVM_FIFO_TRACE
 #define svm_fifo_trace_add(_f, _s, _l, _t)		\
@@ -110,206 +146,691 @@ typedef struct svm_fifo_segment_
 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);
 
-static inline u32
-svm_fifo_max_dequeue (svm_fifo_t * f)
+/**
+ * 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)
 {
-  return f->cursize;
+  /* load-relaxed: consumer owned index */
+  *head = f->head;
+  /* load-acq: consumer foreign index (paired with store-rel in producer) */
+  *tail = clib_atomic_load_acq_n (&f->tail);
 }
 
-static inline int
-svm_fifo_is_full (svm_fifo_t * f)
+/** 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)
 {
-  return (f->cursize == f->nitems);
+  /* load relaxed: producer owned index */
+  *tail = f->tail;
+  /* load-acq: producer foreign index (paired with store-rel in consumer) */
+  *head = clib_atomic_load_acq_n (&f->head);
 }
 
-static inline int
-svm_fifo_is_empty (svm_fifo_t * f)
+/**
+ * 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)
 {
-  return (f->cursize == 0);
+  /* load-acq : consumer foreign index (paired with store-rel) */
+  *tail = clib_atomic_load_acq_n (&f->tail);
+  /* load-acq : producer foriegn index (paired with store-rel) */
+  *head = clib_atomic_load_acq_n (&f->head);
 }
 
+/**
+ * Distance to a from b, i.e., a - b in the fifo
+ *
+ * Internal function.
+ */
 static inline u32
-svm_fifo_max_enqueue (svm_fifo_t * f)
+f_distance_to (svm_fifo_t * f, u32 a, u32 b)
 {
-  return f->nitems - svm_fifo_max_dequeue (f);
+  return ((f->size + a - b) % f->size);
 }
 
-static inline int
-svm_fifo_has_event (svm_fifo_t * f)
+/**
+ * Distance from a to b, i.e., b - a in the fifo
+ *
+ * Internal function.
+ */
+static inline u32
+f_distance_from (svm_fifo_t * f, u32 a, u32 b)
 {
-  return f->has_event;
+  return ((f->size + b - a) % f->size);
 }
 
-static inline u8
-svm_fifo_has_ooo_data (svm_fifo_t * f)
+/**
+ * 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 f->ooos_list_head != OOO_SEGMENT_INVALID_INDEX;
+  return (head <= tail ? tail - head : f->size + tail - head);
 }
 
 /**
- * Sets fifo event flag.
+ * Fifo free bytes, i.e., number of free bytes
  *
- * Also acts as a release barrier.
+ * Internal function
+ */
+static inline u32
+f_free_count (svm_fifo_t * f, u32 head, u32 tail)
+{
+  return (f->nitems - f_cursize (f, head, tail));
+}
+
+/**
+ * Try to shrink fifo size.
  *
- * @return 1 if flag was not set.
+ * Internal function.
  */
-always_inline u8
-svm_fifo_set_event (svm_fifo_t * f)
+void svm_fifo_try_shrink (svm_fifo_t * f, u32 head, u32 tail);
+
+/**
+ * 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_create (u32 size);
+/**
+ * Initialize 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);
+/**
+ * Grow fifo size by adding chunk to chunk list
+ *
+ * If fifos are allocated on a segment, this should be called with
+ * the segment's heap pushed.
+ *
+ * @param f	fifo to be extended
+ * @param c 	chunk or linked list of chunks to be added
+ */
+void svm_fifo_add_chunk (svm_fifo_t * f, svm_fifo_chunk_t * c);
+/**
+ * Request to reduce fifo size by amount of bytes
+ *
+ * Because the producer might be enqueuing data when this is called, the
+ * actual size update is only applied when producer tries to enqueue new
+ * data, unless @param try_shrink is set.
+ *
+ * @param f		fifo
+ * @param len		number of bytes to remove from fifo. The actual number
+ * 			of bytes to be removed will be less or equal to this
+ * 			value.
+ * @param try_shrink	flg to indicate if it's safe to try to shrink fifo
+ * 			size. It should be set only if this is called by the
+ * 			producer of if the producer is not using the fifo
+ * @return		actual length fifo size will be reduced by
+ */
+int svm_fifo_reduce_size (svm_fifo_t * f, u32 len, u8 try_shrink);
+/**
+ * Removes chunks that are after fifo end byte
+ *
+ * Needs to be called with segment heap pushed.
+ *
+ * @param f fifo
+ */
+svm_fifo_chunk_t *svm_fifo_collect_chunks (svm_fifo_t * f);
+/**
+ * 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);
+/**
+ * Overwrite fifo head with new data
+ *
+ * This should be typically used by dgram transport protocols that need
+ * to update the dgram header after dequeueing 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.
+ *
+ * @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);
+int svm_fifo_segments (svm_fifo_t * f, svm_fifo_seg_t * fs);
+void svm_fifo_segments_free (svm_fifo_t * f, svm_fifo_seg_t * fs);
+/**
+ * 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);
+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)
 {
-  /* return __sync_lock_test_and_set (&f->has_event, 1) == 0;
-     return __sync_bool_compare_and_swap (&f->has_event, 0, 1); */
-  return !__atomic_exchange_n (&f->has_event, 1, __ATOMIC_RELEASE);
+  u32 tail, head;
+  f_load_head_tail_cons (f, &head, &tail);
+  return f_cursize (f, head, tail);
 }
 
 /**
- * Unsets fifo event flag.
+ * Fifo max bytes to dequeue optimized for producer
  *
- * Also acts as a release barrier.
+ * @param f	fifo
+ * @return	max number of bytes that can be dequeued
  */
-always_inline void
-svm_fifo_unset_event (svm_fifo_t * f)
+static inline u32
+svm_fifo_max_dequeue_prod (svm_fifo_t * f)
 {
-  __sync_lock_release (&f->has_event);
+  u32 tail, head;
+  f_load_head_tail_prod (f, &head, &tail);
+  return f_cursize (f, head, tail);
 }
 
-static inline void
-svm_fifo_set_want_tx_evt (svm_fifo_t * f, u8 want_evt)
+/**
+ * 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)
 {
-  f->want_tx_evt = want_evt;
+  u32 tail, head;
+  f_load_head_tail_all_acq (f, &head, &tail);
+  return f_cursize (f, head, tail);
 }
 
-static inline u8
-svm_fifo_want_tx_evt (svm_fifo_t * f)
+/**
+ * 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 f->want_tx_evt;
+  return (svm_fifo_max_dequeue_prod (f) == f->nitems);
 }
 
-svm_fifo_t *svm_fifo_create (u32 data_size_in_bytes);
-void svm_fifo_free (svm_fifo_t * f);
+/* 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->nitems);
+}
 
-int svm_fifo_enqueue_nowait (svm_fifo_t * f, u32 max_bytes,
-			     const u8 * copy_from_here);
-int svm_fifo_enqueue_with_offset (svm_fifo_t * f, u32 offset,
-				  u32 required_bytes, u8 * copy_from_here);
-int svm_fifo_dequeue_nowait (svm_fifo_t * f, u32 max_bytes, u8 * copy_here);
+/**
+ * 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);
+}
 
-int svm_fifo_peek (svm_fifo_t * f, u32 offset, u32 max_bytes, u8 * copy_here);
-int svm_fifo_dequeue_drop (svm_fifo_t * f, u32 max_bytes);
-void svm_fifo_dequeue_drop_all (svm_fifo_t * f);
-int svm_fifo_segments (svm_fifo_t * f, svm_fifo_segment_t * fs);
-void svm_fifo_segments_free (svm_fifo_t * f, svm_fifo_segment_t * fs);
-u32 svm_fifo_number_ooo_segments (svm_fifo_t * f);
-ooo_segment_t *svm_fifo_first_ooo_segment (svm_fifo_t * f);
-void svm_fifo_init_pointers (svm_fifo_t * f, u32 pointer);
-void svm_fifo_overwrite_head (svm_fifo_t * f, u8 * data, u32 len);
+/**
+ * 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);
+}
 
-format_function_t format_svm_fifo;
+/**
+ * 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);
+}
 
-always_inline ooo_segment_t *
-svm_fifo_newest_ooo_segment (svm_fifo_t * f)
+/**
+ * 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)
 {
-  if (f->ooos_newest == OOO_SEGMENT_INVALID_INDEX)
-    return 0;
-  return pool_elt_at_index (f->ooo_segments, f->ooos_newest);
+  u32 head, tail;
+  f_load_head_tail_all_acq (f, &head, &tail);
+  return head > tail;
 }
 
-always_inline void
-svm_fifo_newest_ooo_segment_reset (svm_fifo_t * f)
+/**
+ * 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)
 {
-  f->ooos_newest = OOO_SEGMENT_INVALID_INDEX;
+  u32 head, tail;
+  f_load_head_tail_prod (f, &head, &tail);
+  if (PREDICT_FALSE (f->flags & SVM_FIFO_F_SHRINK))
+    svm_fifo_try_shrink (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)
+{
+  u32 head, tail;
+  f_load_head_tail_all_acq (f, &head, &tail);
+  if (PREDICT_FALSE (f->flags & SVM_FIFO_F_SHRINK))
+    svm_fifo_try_shrink (f, head, tail);
+  return f_free_count (f, head, tail);
 }
 
 /**
  * Max contiguous chunk of data that can be read
  */
-always_inline u32
+static inline u32
 svm_fifo_max_read_chunk (svm_fifo_t * f)
 {
-  return ((f->tail > f->head) ? (f->tail - f->head) : (f->nitems - f->head));
+  u32 head, tail;
+  f_load_head_tail_cons (f, &head, &tail);
+  return tail >= head ? (tail - head) : (f->size - head);
 }
 
 /**
  * Max contiguous chunk of data that can be written
  */
-always_inline u32
+static inline u32
 svm_fifo_max_write_chunk (svm_fifo_t * f)
 {
-  return ((f->tail >= f->head) ? (f->nitems - f->tail) : (f->head - f->tail));
+  u32 head, tail;
+  f_load_head_tail_prod (f, &head, &tail);
+  return tail > head ? f->size - tail : f_free_count (f, head, tail);
+}
+
+static inline u8 *
+svm_fifo_head (svm_fifo_t * f)
+{
+  /* load-relaxed: consumer owned index */
+  return (f->head_chunk->data + (f->head - f->head_chunk->start_byte));
+}
+
+static inline u8 *
+svm_fifo_tail (svm_fifo_t * f)
+{
+  /* load-relaxed: producer owned index */
+  return (f->tail_chunk->data + (f->tail - f->tail_chunk->start_byte));
+}
+
+static inline u8
+svm_fifo_n_subscribers (svm_fifo_t * f)
+{
+  return f->n_subscribers;
 }
 
 /**
- * Advance tail pointer
+ * Check if fifo has out-of-order data
  *
- * Useful for moving tail pointer after external enqueue.
+ * @param f	fifo
+ * @return	1 if fifo has ooo data, 0 otherwise
  */
-always_inline void
-svm_fifo_enqueue_nocopy (svm_fifo_t * f, u32 bytes)
+static inline u8
+svm_fifo_has_ooo_data (svm_fifo_t * f)
 {
-  ASSERT (bytes <= svm_fifo_max_enqueue (f));
-  f->tail = (f->tail + bytes) % f->nitems;
-  f->cursize += bytes;
+  return f->ooos_list_head != OOO_SEGMENT_INVALID_INDEX;
 }
 
-always_inline u8 *
-svm_fifo_head (svm_fifo_t * f)
+static inline ooo_segment_t *
+svm_fifo_newest_ooo_segment (svm_fifo_t * f)
 {
-  return (f->data + f->head);
+  if (f->ooos_newest == OOO_SEGMENT_INVALID_INDEX)
+    return 0;
+  return pool_elt_at_index (f->ooo_segments, f->ooos_newest);
 }
 
-always_inline u8 *
-svm_fifo_tail (svm_fifo_t * f)
+static inline void
+svm_fifo_newest_ooo_segment_reset (svm_fifo_t * f)
 {
-  return (f->data + f->tail);
+  f->ooos_newest = OOO_SEGMENT_INVALID_INDEX;
 }
 
-always_inline u32
-ooo_segment_distance_from_tail (svm_fifo_t * f, u32 pos)
+static inline u32
+ooo_segment_offset_prod (svm_fifo_t * f, ooo_segment_t * s)
 {
-  /* Ambiguous. Assumption is that ooo segments don't touch tail */
-  if (PREDICT_FALSE (pos == f->tail && f->tail == f->head))
-    return f->nitems;
+  u32 tail;
+  /* load-relaxed: producer owned index */
+  tail = f->tail;
 
-  return (((f->nitems + pos) - f->tail) % f->nitems);
+  return f_distance_to (f, s->start, tail);
 }
 
-always_inline u32
-ooo_segment_distance_to_tail (svm_fifo_t * f, u32 pos)
+static inline u32
+ooo_segment_length (svm_fifo_t * f, ooo_segment_t * s)
 {
-  return (((f->nitems + f->tail) - pos) % f->nitems);
+  return s->length;
 }
 
-always_inline u32
-ooo_segment_offset (svm_fifo_t * f, ooo_segment_t * s)
+/**
+ * Check if fifo has io event
+ *
+ * @param f	fifo
+ * @return	1 if fifo has event, 0 otherwise
+ */
+static inline int
+svm_fifo_has_event (svm_fifo_t * f)
 {
-  return ooo_segment_distance_from_tail (f, s->start);
+  return f->has_event;
 }
 
-always_inline u32
-ooo_segment_end_offset (svm_fifo_t * f, ooo_segment_t * s)
+/**
+ * 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)
 {
-  return ooo_segment_distance_from_tail (f, s->start) + s->length;
+  return !clib_atomic_swap_rel_n (&f->has_event, 1);
 }
 
-always_inline u32
-ooo_segment_length (svm_fifo_t * f, ooo_segment_t * s)
+/**
+ * Unset fifo event flag.
+ *
+ * Forces acquire semantics
+ *
+ * @param f	fifo
+ */
+always_inline void
+svm_fifo_unset_event (svm_fifo_t * f)
 {
-  return s->length;
+  clib_atomic_swap_acq_n (&f->has_event, 0);
 }
 
-always_inline ooo_segment_t *
-ooo_segment_get_prev (svm_fifo_t * f, ooo_segment_t * s)
+/**
+ * Set specific want tx notification flag
+ *
+ * For list of flags see @ref svm_fifo_tx_ntf_t
+ *
+ * @param f		fifo
+ * @param ntf_type	type of notification requested
+ */
+static inline void
+svm_fifo_add_want_tx_ntf (svm_fifo_t * f, u8 ntf_type)
 {
-  if (s->prev == OOO_SEGMENT_INVALID_INDEX)
-    return 0;
-  return pool_elt_at_index (f->ooo_segments, s->prev);
+  f->want_tx_ntf |= ntf_type;
 }
 
-always_inline ooo_segment_t *
-ooo_segment_next (svm_fifo_t * f, ooo_segment_t * s)
+/**
+ * Clear specific want tx notification flag
+ *
+ * For list of flags see @ref svm_fifo_tx_ntf_t
+ *
+ * @param f 		fifo
+ * @param ntf_type	type of notification to be cleared
+ */
+static inline void
+svm_fifo_del_want_tx_ntf (svm_fifo_t * f, u8 ntf_type)
 {
-  if (s->next == OOO_SEGMENT_INVALID_INDEX)
+  f->want_tx_ntf &= ~ntf_type;
+}
+
+/**
+ * Clear the want tx notification flag and set has tx notification
+ *
+ * Should be used after enqueuing a tx event. This clears the
+ * SVM_FIFO_WANT_TX_NOTIF flag but it does not clear
+ * SVM_FIFO_WANT_TX_NOTIF_IF_FULL. If the latter was set, has_tx_ntf is
+ * set to avoid enqueueing tx events for for all dequeue operations until
+ * it is manually cleared.
+ *
+ * @param f	fifo
+ */
+static inline void
+svm_fifo_clear_tx_ntf (svm_fifo_t * f)
+{
+  /* Set the flag if want_tx_notif_if_full was the only ntf requested */
+  f->has_tx_ntf = f->want_tx_ntf == SVM_FIFO_WANT_TX_NOTIF_IF_FULL;
+  svm_fifo_del_want_tx_ntf (f, SVM_FIFO_WANT_TX_NOTIF);
+}
+
+/**
+ * Clear has tx notification flag
+ *
+ * The fifo generates only one event per SVM_FIFO_WANT_TX_NOTIF_IF_FULL
+ * request and sets has_tx_ntf. To received new events the flag must be
+ * cleared using this function.
+ *
+ * @param f	fifo
+ */
+static inline void
+svm_fifo_reset_tx_ntf (svm_fifo_t * f)
+{
+  f->has_tx_ntf = 0;
+}
+
+/**
+ * Check if fifo needs tx notification
+ *
+ * Determines based on tx notification request flags and state of the fifo if
+ * a tx io event should be generated.
+ *
+ * @param f		fifo
+ * @param n_last_deq	number of bytes last dequeued
+ * @return		1 if tx io event should be generated, 0 otherwise
+ */
+static inline u8
+svm_fifo_needs_tx_ntf (svm_fifo_t * f, u32 n_last_deq)
+{
+  u8 want_ntf = f->want_tx_ntf;
+
+  if (PREDICT_TRUE (want_ntf == SVM_FIFO_NO_TX_NOTIF))
     return 0;
-  return pool_elt_at_index (f->ooo_segments, s->next);
+  else if (want_ntf & SVM_FIFO_WANT_TX_NOTIF)
+    return 1;
+  else if (want_ntf & SVM_FIFO_WANT_TX_NOTIF_IF_FULL)
+    {
+      u32 max_deq = svm_fifo_max_dequeue_cons (f);
+      u32 nitems = f->nitems;
+      if (!f->has_tx_ntf && max_deq < nitems
+	  && max_deq + n_last_deq >= nitems)
+	return 1;
+
+      return 0;
+    }
+  return 0;
 }
 
 #endif /* __included_ssvm_fifo_h__ */