<snip>
>
> For rings with producer/consumer in RTE_RING_SYNC_ST,
> RTE_RING_SYNC_MT_HTS mode, provide an ability to split enqueue/dequeue
> operation into two phases:
> - enqueue/dequeue start
> - enqueue/dequeue finish
> That allows user to inspect objects in the ring without removing them from it
> (aka MT safe peek).
>
> Signed-off-by: Konstantin Ananyev <konstantin.anan...@intel.com>
> ---
> lib/librte_ring/Makefile | 1 +
> lib/librte_ring/meson.build | 1 +
> lib/librte_ring/rte_ring_c11_mem.h | 44 +++
> lib/librte_ring/rte_ring_elem.h | 4 +
> lib/librte_ring/rte_ring_generic.h | 48 ++++
> lib/librte_ring/rte_ring_hts_generic.h | 47 ++-
> lib/librte_ring/rte_ring_peek.h | 379 +++++++++++++++++++++++++
> 7 files changed, 519 insertions(+), 5 deletions(-) create mode 100644
> lib/librte_ring/rte_ring_peek.h
>
> diff --git a/lib/librte_ring/Makefile b/lib/librte_ring/Makefile index
> 6fe500f0d..5f8662737 100644
> --- a/lib/librte_ring/Makefile
> +++ b/lib/librte_ring/Makefile
> @@ -22,6 +22,7 @@ SYMLINK-$(CONFIG_RTE_LIBRTE_RING)-include :=
> rte_ring.h \
> rte_ring_hts.h \
> rte_ring_hts_elem.h \
> rte_ring_hts_generic.h \
> + rte_ring_peek.h \
> rte_ring_rts.h \
> rte_ring_rts_elem.h \
> rte_ring_rts_generic.h
> diff --git a/lib/librte_ring/meson.build b/lib/librte_ring/meson.build index
> 8e86e037a..f5f84dc6e 100644
> --- a/lib/librte_ring/meson.build
> +++ b/lib/librte_ring/meson.build
> @@ -9,6 +9,7 @@ headers = files('rte_ring.h',
> 'rte_ring_hts.h',
> 'rte_ring_hts_elem.h',
> 'rte_ring_hts_generic.h',
> + 'rte_ring_peek.h',
> 'rte_ring_rts.h',
> 'rte_ring_rts_elem.h',
> 'rte_ring_rts_generic.h')
> diff --git a/lib/librte_ring/rte_ring_c11_mem.h
> b/lib/librte_ring/rte_ring_c11_mem.h
> index 0fb73a337..bb3096721 100644
> --- a/lib/librte_ring/rte_ring_c11_mem.h
> +++ b/lib/librte_ring/rte_ring_c11_mem.h
> @@ -10,6 +10,50 @@
> #ifndef _RTE_RING_C11_MEM_H_
> #define _RTE_RING_C11_MEM_H_
>
> +/**
> + * @internal get current tail value.
> + * This function should be used only for single thread producer/consumer.
> + * Check that user didn't request to move tail above the head.
Do we need this check? This could be a data path function, we could document a
warning and leave it to the users to provide the correct value.
> + * In that situation:
> + * - return zero, that will cause abort any pending changes and
> + * return head to its previous position.
> + * - throw an assert in debug mode.
> + */
> +static __rte_always_inline uint32_t
> +__rte_ring_st_get_tail(struct rte_ring_headtail *ht, uint32_t *tail,
> + uint32_t num)
> +{
> + uint32_t h, n, t;
> +
> + h = ht->head;
> + t = ht->tail;
> + n = h - t;
> +
> + RTE_ASSERT(n >= num);
> + num = (n >= num) ? num : 0;
> +
> + *tail = h;
> + return num;
> +}
> +
> +/**
> + * @internal set new values for head and tail.
> + * This function should be used only for single thread producer/consumer.
> + * Should be used only in conjunction with __rte_ring_st_get_tail.
> + */
> +static __rte_always_inline void
> +__rte_ring_st_set_head_tail(struct rte_ring_headtail *ht, uint32_t tail,
> + uint32_t num, uint32_t enqueue)
> +{
> + uint32_t pos;
> +
> + RTE_SET_USED(enqueue);
> +
> + pos = tail + num;
> + ht->head = pos;
> + __atomic_store_n(&ht->tail, pos, __ATOMIC_RELEASE); }
> +
> static __rte_always_inline void
> update_tail(struct rte_ring_headtail *ht, uint32_t old_val, uint32_t new_val,
> uint32_t single, uint32_t enqueue)
> diff --git a/lib/librte_ring/rte_ring_elem.h b/lib/librte_ring/rte_ring_elem.h
> index 010a564c1..5bf7c1c1b 100644
> --- a/lib/librte_ring/rte_ring_elem.h
> +++ b/lib/librte_ring/rte_ring_elem.h
> @@ -1083,6 +1083,10 @@ rte_ring_dequeue_burst_elem(struct rte_ring *r,
> void *obj_table,
> return 0;
> }
>
> +#ifdef ALLOW_EXPERIMENTAL_API
> +#include <rte_ring_peek.h>
> +#endif
> +
> #ifdef __cplusplus
> }
> #endif
> diff --git a/lib/librte_ring/rte_ring_generic.h
> b/lib/librte_ring/rte_ring_generic.h
> index 953cdbbd5..9f5fdf13b 100644
> --- a/lib/librte_ring/rte_ring_generic.h
> +++ b/lib/librte_ring/rte_ring_generic.h
> @@ -10,6 +10,54 @@
> #ifndef _RTE_RING_GENERIC_H_
> #define _RTE_RING_GENERIC_H_
>
> +/**
> + * @internal get current tail value.
> + * This function should be used only for single thread producer/consumer.
> + * Check that user didn't request to move tail above the head.
> + * In that situation:
> + * - return zero, that will cause abort any pending changes and
> + * return head to its previous position.
> + * - throw an assert in debug mode.
> + */
> +static __rte_always_inline uint32_t
> +__rte_ring_st_get_tail(struct rte_ring_headtail *ht, uint32_t *tail,
> + uint32_t num)
> +{
> + uint32_t h, n, t;
> +
> + h = ht->head;
> + t = ht->tail;
> + n = h - t;
> +
> + RTE_ASSERT(n >= num);
> + num = (n >= num) ? num : 0;
> +
> + *tail = h;
> + return num;
> +}
> +
> +/**
> + * @internal set new values for head and tail.
> + * This function should be used only for single thread producer/consumer.
> + * Should be used only in conjunction with __rte_ring_st_get_tail.
> + */
> +static __rte_always_inline void
> +__rte_ring_st_set_head_tail(struct rte_ring_headtail *ht, uint32_t tail,
> + uint32_t num, uint32_t enqueue)
> +{
> + uint32_t pos;
> +
> + pos = tail + num;
> +
> + if (enqueue)
> + rte_smp_wmb();
> + else
> + rte_smp_rmb();
> +
> + ht->head = pos;
> + ht->tail = pos;
> +}
> +
> static __rte_always_inline void
> update_tail(struct rte_ring_headtail *ht, uint32_t old_val, uint32_t new_val,
> uint32_t single, uint32_t enqueue)
> diff --git a/lib/librte_ring/rte_ring_hts_generic.h
> b/lib/librte_ring/rte_ring_hts_generic.h
> index da08f1d94..8e699c006 100644
> --- a/lib/librte_ring/rte_ring_hts_generic.h
> +++ b/lib/librte_ring/rte_ring_hts_generic.h
> @@ -18,9 +18,38 @@
> * For more information please refer to <rte_ring_hts.h>.
> */
>
> +/**
> + * @internal get current tail value.
> + * Check that user didn't request to move tail above the head.
> + * In that situation:
> + * - return zero, that will cause abort any pending changes and
> + * return head to its previous position.
> + * - throw an assert in debug mode.
> + */
> +static __rte_always_inline uint32_t
> +__rte_ring_hts_get_tail(struct rte_ring_hts_headtail *ht, uint32_t *tail,
> + uint32_t num)
> +{
> + uint32_t n;
> + union rte_ring_ht_pos p;
> +
> + p.raw = rte_atomic64_read((rte_atomic64_t *)(uintptr_t)&ht-
> >ht.raw);
> + n = p.pos.head - p.pos.tail;
> +
> + RTE_ASSERT(n >= num);
> + num = (n >= num) ? num : 0;
> +
> + *tail = p.pos.tail;
> + return num;
> +}
> +
> +/**
> + * @internal set new values for head and tail as one atomic 64 bit operation.
> + * Should be used only in conjunction with __rte_ring_hts_get_tail.
> + */
> static __rte_always_inline void
> -__rte_ring_hts_update_tail(struct rte_ring_hts_headtail *ht, uint32_t num,
> - uint32_t enqueue)
> +__rte_ring_hts_set_head_tail(struct rte_ring_hts_headtail *ht, uint32_t tail,
> + uint32_t num, uint32_t enqueue)
> {
> union rte_ring_ht_pos p;
>
> @@ -29,14 +58,22 @@ __rte_ring_hts_update_tail(struct
> rte_ring_hts_headtail *ht, uint32_t num,
> else
> rte_smp_rmb();
>
> - p.raw = rte_atomic64_read((rte_atomic64_t *)(uintptr_t)&ht-
> >ht.raw);
> -
> - p.pos.head = p.pos.tail + num;
> + p.pos.head = tail + num;
> p.pos.tail = p.pos.head;
>
> rte_atomic64_set((rte_atomic64_t *)(uintptr_t)&ht->ht.raw, p.raw); }
>
> +static __rte_always_inline void
> +__rte_ring_hts_update_tail(struct rte_ring_hts_headtail *ht, uint32_t num,
> + uint32_t enqueue)
> +{
> + uint32_t tail;
> +
> + num = __rte_ring_hts_get_tail(ht, &tail, num);
> + __rte_ring_hts_set_head_tail(ht, tail, num, enqueue); }
> +
> /**
> * @internal waits till tail will become equal to head.
> * Means no writer/reader is active for that ring.
> diff --git a/lib/librte_ring/rte_ring_peek.h b/lib/librte_ring/rte_ring_peek.h
> new file mode 100644 index 000000000..baefd2f7b
> --- /dev/null
> +++ b/lib/librte_ring/rte_ring_peek.h
> @@ -0,0 +1,379 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + *
> + * Copyright (c) 2010-2017 Intel Corporation
> + * Copyright (c) 2007-2009 Kip Macy km...@freebsd.org
> + * All rights reserved.
> + * Derived from FreeBSD's bufring.h
> + * Used as BSD-3 Licensed with permission from Kip Macy.
> + */
> +
> +#ifndef _RTE_RING_PEEK_H_
> +#define _RTE_RING_PEEK_H_
> +
> +/**
> + * @file
> + * @b EXPERIMENTAL: this API may change without prior notice
> + * It is not recommended to include this file directly.
> + * Please include <rte_ring_elem.h> instead.
> + *
> + * Ring Peek AP
^^^ API
> + * Introduction of rte_ring with serialized producer/consumer (HTS sync
> +mode)
> + * makes possible to split public enqueue/dequeue API into two phases:
> + * - enqueue/dequeue start
> + * - enqueue/dequeue finish
> + * That allows user to inspect objects in the ring without removing
> +them
> + * from it (aka MT safe peek).
> + * Note that right now this new API is avaialble only for two sync modes:
> + * 1) Single Producer/Single Consumer (RTE_RING_SYNC_ST)
> + * 2) Serialized Producer/Serialized Consumer (RTE_RING_SYNC_MT_HTS).
> + * It is a user responsibility to create/init ring with appropriate
> +sync
> + * modes selected.
> + * As an example:
> + * // read 1 elem from the ring:
> + * n = rte_ring_hts_dequeue_bulk_start(ring, &obj, 1, NULL);
> + * if (n != 0) {
> + * //examine object
> + * if (object_examine(obj) == KEEP)
> + * //decided to keep it in the ring.
> + * rte_ring_hts_dequeue_finish(ring, 0);
> + * else
> + * //decided to remove it from the ring.
> + * rte_ring_hts_dequeue_finish(ring, n);
> + * }
> + * Note that between _start_ and _finish_ the ring is sort of locked -
^^^^^^^^^^^^^^^^^^^^ - 'locked' can mean different to different people, may
be remove this, the next sentence anyway has the description
> + * none other thread can proceed with enqueue(/dequeue) operation till
^^^^ no
> + * _finish_ will complete.
^^^^^^^^^^^ completes
> + */
> +
> +#ifdef __cplusplus
> +extern "C" {
> +#endif
> +
<snip>
> +
> +/**
> + * Start to enqueue several objects on the ring.
> + * Note that no actual objects are put in the queue by this function,
> + * it just reserves for user such ability.
> + * User has to call appropriate enqueue_finish() to copy objects into
> +the
> + * queue and complete given enqueue operation.
> + *
> + * @param r
> + * A pointer to the ring structure.
> + * @param n
> + * The number of objects to add in the ring from the obj_table.
> + * @param free_space
> + * if non-NULL, returns the amount of space in the ring after the
> + * enqueue operation has finished.
> + * @return
> + * The number of objects that can be enqueued, either 0 or n
> + */
> +__rte_experimental
> +static __rte_always_inline unsigned int
> +rte_ring_enqueue_bulk_start(struct rte_ring *r, unsigned int n,
> + unsigned int *free_space)
If one wants to use _elem_ APIs for ring peek, a combination of legacy API
(format) and a _elem_ API is required.
For ex:
rte_ring_enqueue_bulk_start
rte_ring_enqueue_elem_finish
I understand why you have done this. I think this is getting somewhat too
inconsistent.
> +{
> + return __rte_ring_do_enqueue_start(r, n, RTE_RING_QUEUE_FIXED,
> + free_space);
> +}
> +
<snip>
> +
> +/**
> + * Start to dequeue several objects from the ring.
> + * Note that user has to call appropriate dequeue_finish()
> + * to complete given dequeue operation and actually remove objects the ring.
> + *
> + * @param r
> + * A pointer to the ring structure.
> + * @param obj_table
> + * A pointer to a table of void * pointers (objects) that will be filled.
> + * @param esize
> + * The size of ring element, in bytes. It must be a multiple of 4.
> + * This must be the same value used while creating the ring. Otherwise
> + * the results are undefined.
> + * @param n
> + * The number of objects to dequeue from the ring to the obj_table.
> + * @param available
> + * If non-NULL, returns the number of remaining ring entries after the
> + * dequeue has finished.
> + * @return
> + * Actual number of objects dequeued.
> + */
> +__rte_experimental
> +static __rte_always_inline unsigned int
> +rte_ring_dequeue_bulk_start(struct rte_ring *r, void **obj_table,
> + unsigned int n, unsigned int *available) {
Should this in a separate file? (similar to rte_ring.h and rte_ring_elem.h)
> + return rte_ring_dequeue_bulk_elem_start(r, obj_table,
> sizeof(uintptr_t),
> + n, available);
> +}
> +
> +/**
> + * Start to dequeue several objects from the ring.
> + * Note that user has to call appropriate dequeue_finish()
> + * to complete given dequeue operation and actually remove objects the ring.
> + *
> + * @param r
> + * A pointer to the ring structure.
> + * @param obj_table
> + * A pointer to a table of void * pointers (objects) that will be filled.
Minor, update this to indicate generic objects. Can be copied from
rte_ring_elem.h.
> + * @param esize
> + * The size of ring element, in bytes. It must be a multiple of 4.
> + * This must be the same value used while creating the ring. Otherwise
> + * the results are undefined.
> + * @param n
> + * The number of objects to dequeue from the ring to the obj_table.
> + * @param available
> + * If non-NULL, returns the number of remaining ring entries after the
> + * dequeue has finished.
> + * @return
> + * The actual number of objects dequeued.
> + */
> +__rte_experimental
> +static __rte_always_inline unsigned int
> +rte_ring_dequeue_burst_elem_start(struct rte_ring *r, void **obj_table,
> + unsigned int esize, unsigned int n, unsigned int *available) {
> + return __rte_ring_do_dequeue_start(r, obj_table, esize, n,
> + RTE_RING_QUEUE_VARIABLE, available); }
> +
<snip>
> +
> +#ifdef __cplusplus
> +}
> +#endif
> +
> +#endif /* _RTE_RING_PEEK_H_ */
> --
> 2.17.1
