[v3,2/5] lib/ring: add zero copy APIs
diff mbox series

Message ID 20201023044343.13462-3-honnappa.nagarahalli@arm.com
State Superseded
Delegated to: David Marchand
Headers show
Series
  • lib/ring: add zero copy APIs
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Context Check Description
ci/checkpatch success coding style OK

Commit Message

Honnappa Nagarahalli Oct. 23, 2020, 4:43 a.m. UTC
Add zero-copy APIs. These APIs provide the capability to
copy the data to/from the ring memory directly, without
having a temporary copy (for ex: an array of mbufs on
the stack). Use cases that involve copying large amount
of data to/from the ring can benefit from these APIs.

Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
---
 lib/librte_ring/meson.build        |   1 +
 lib/librte_ring/rte_ring_elem.h    |   1 +
 lib/librte_ring/rte_ring_peek_zc.h | 542 +++++++++++++++++++++++++++++
 3 files changed, 544 insertions(+)
 create mode 100644 lib/librte_ring/rte_ring_peek_zc.h

Comments

Ananyev, Konstantin Oct. 23, 2020, 1:59 p.m. UTC | #1
> 
> Add zero-copy APIs. These APIs provide the capability to
> copy the data to/from the ring memory directly, without
> having a temporary copy (for ex: an array of mbufs on
> the stack). Use cases that involve copying large amount
> of data to/from the ring can benefit from these APIs.

LGTM in general.
Few nits, see below.

> 
> Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> Reviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
> ---
>  lib/librte_ring/meson.build        |   1 +
>  lib/librte_ring/rte_ring_elem.h    |   1 +
>  lib/librte_ring/rte_ring_peek_zc.h | 542 +++++++++++++++++++++++++++++
>  3 files changed, 544 insertions(+)
>  create mode 100644 lib/librte_ring/rte_ring_peek_zc.h

Need to update documentation: PG and RN.

> 
> diff --git a/lib/librte_ring/meson.build b/lib/librte_ring/meson.build
> index 31c0b4649..36fdcb6a5 100644
> --- a/lib/librte_ring/meson.build
> +++ b/lib/librte_ring/meson.build
> @@ -11,5 +11,6 @@ headers = files('rte_ring.h',
>  		'rte_ring_hts_c11_mem.h',
>  		'rte_ring_peek.h',
>  		'rte_ring_peek_c11_mem.h',
> +		'rte_ring_peek_zc.h',
>  		'rte_ring_rts.h',
>  		'rte_ring_rts_c11_mem.h')
> diff --git a/lib/librte_ring/rte_ring_elem.h b/lib/librte_ring/rte_ring_elem.h
> index 938b398fc..7034d29c0 100644
> --- a/lib/librte_ring/rte_ring_elem.h
> +++ b/lib/librte_ring/rte_ring_elem.h
> @@ -1079,6 +1079,7 @@ rte_ring_dequeue_burst_elem(struct rte_ring *r, void *obj_table,
> 
>  #ifdef ALLOW_EXPERIMENTAL_API
>  #include <rte_ring_peek.h>
> +#include <rte_ring_peek_zc.h>
>  #endif
> 
>  #include <rte_ring.h>
> diff --git a/lib/librte_ring/rte_ring_peek_zc.h b/lib/librte_ring/rte_ring_peek_zc.h
> new file mode 100644
> index 000000000..9db2d343f
> --- /dev/null
> +++ b/lib/librte_ring/rte_ring_peek_zc.h
> @@ -0,0 +1,542 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + *
> + * Copyright (c) 2020 Arm Limited
> + * Copyright (c) 2007-2009 Kip Macy kmacy@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_ZC_H_
> +#define _RTE_RING_PEEK_ZC_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 Zero Copy APIs
> + * These APIs make it possible to split public enqueue/dequeue API
> + * into 3 parts:
> + * - enqueue/dequeue start
> + * - copy data to/from the ring
> + * - enqueue/dequeue finish
> + * Along with the advantages of the peek APIs, these APIs provide the ability
> + * to avoid copying of the data to temporary area (for ex: array of mbufs
> + * on the stack).
> + *
> + * Note that currently these APIs are available 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 user's responsibility to create/init ring with appropriate sync
> + * modes selected.
> + *
> + * Following are some examples showing the API usage.
> + * 1)
> + * struct elem_obj {uint64_t a; uint32_t b, c;};
> + * struct elem_obj *obj;
> + *
> + * // Create ring with sync type RTE_RING_SYNC_ST or RTE_RING_SYNC_MT_HTS
> + * // Reserve space on the ring
> + * n = rte_ring_enqueue_zc_bulk_elem_start(r, sizeof(elem_obj), 1, &zcd, NULL);
> + *
> + * // Produce the data directly on the ring memory
> + * obj = (struct elem_obj *)zcd->ptr1;
> + * obj.a = rte_get_a();

As obj is a pointer, should be obj->a = ...
Same for b and c.

> + * obj.b = rte_get_b();
> + * obj.c = rte_get_c();
> + * rte_ring_enqueue_zc_elem_finish(ring, n);
> + *
> + * 2)
> + * // Create ring with sync type RTE_RING_SYNC_ST or RTE_RING_SYNC_MT_HTS
> + * // Reserve space on the ring
> + * n = rte_ring_enqueue_zc_burst_start(r, 32, &zcd, NULL);
> + *
> + * // Pkt I/O core polls packets from the NIC
> + * if (n == 32)
> + *	nb_rx = rte_eth_rx_burst(portid, queueid, zcd->ptr1, 32);
> + * else
> + *	nb_rx = rte_eth_rx_burst(portid, queueid, zcd->ptr1, zcd->n1);

Hmm, that doesn't look exactly correct to me.
It could be that n == 32, but we still need to do wrap-around.
Shouldn't it be:

If (n != 0) {
	nb_rx = rte_eth_rx_burst(portid, queueid, zcd->ptr1, zcd->n1);
	if (nb_rx == zcd->n1 && nb_rx != n)
		nb_rx += rte_eth_rx_burst(portid, queueid, zcd->ptr2, n - nb_rx);
}

> + *
> + * // Provide packets to the packet processing cores
> + * rte_ring_enqueue_zc_finish(r, nb_rx);
> + *
> + * Note that between _start_ and _finish_ none other thread can proceed
> + * with enqueue/dequeue operation till _finish_ completes.
> + */
> +
> +#ifdef __cplusplus
> +extern "C" {
> +#endif
> +
> +#include <rte_ring_peek_c11_mem.h>
> +
> +/**
> + * Ring zero-copy information structure.
> + *
> + * This structure contains the pointers and length of the space
> + * reserved on the ring storage.
> + */
> +struct rte_ring_zc_data {
> +	/* Pointer to the first space in the ring */
> +	void **ptr1;

Why not just 'void *ptr1;'?
Same for ptr2.

> +	/* Pointer to the second space in the ring if there is wrap-around */
> +	void **ptr2;
> +	/* Number of elements in the first pointer. If this is equal to
> +	 * the number of elements requested, then ptr2 is NULL.
> +	 * Otherwise, subtracting n1 from number of elements requested
> +	 * will give the number of elements available at ptr2.
> +	 */
> +	unsigned int n1;
> +} __rte_cache_aligned;
> +
> +static __rte_always_inline void
> +__rte_ring_get_elem_addr(struct rte_ring *r, uint32_t head,
> +	uint32_t esize, uint32_t num, void **dst1, uint32_t *n1, void **dst2)
> +{
> +	uint32_t idx, scale, nr_idx;
> +	uint32_t *ring = (uint32_t *)&r[1];
> +
> +	/* Normalize to uint32_t */
> +	scale = esize / sizeof(uint32_t);
> +	idx = head & r->mask;
> +	nr_idx = idx * scale;
> +
> +	*dst1 = ring + nr_idx;
> +	*n1 = num;
> +
> +	if (idx + num > r->size) {
> +		*n1 = r->size - idx;
> +		*dst2 = ring;
> +	}

Seems like missing:
else {*dst2 = NULL;}

> +}
> +
> +/**
> + * @internal This function moves prod head value.
> + */
> +static __rte_always_inline unsigned int
> +__rte_ring_do_enqueue_zc_elem_start(struct rte_ring *r, unsigned int esize,
> +		uint32_t n, enum rte_ring_queue_behavior behavior,
> +		struct rte_ring_zc_data *zcd, unsigned int *free_space)
> +{
> +	uint32_t free, head, next;
> +
> +	switch (r->prod.sync_type) {
> +	case RTE_RING_SYNC_ST:
> +		n = __rte_ring_move_prod_head(r, RTE_RING_SYNC_ST, n,
> +			behavior, &head, &next, &free);
> +		__rte_ring_get_elem_addr(r, head, esize, n, (void **)&zcd->ptr1,

If you change ptr1, ptr2 to be just 'void *', then probably no extra type-cast
will be needed here. 

> +			&zcd->n1, (void **)&zcd->ptr2);
> +		break;
> +	case RTE_RING_SYNC_MT_HTS:
> +		n = __rte_ring_hts_move_prod_head(r, n, behavior, &head, &free);
> +		__rte_ring_get_elem_addr(r, head, esize, n, (void **)&zcd->ptr1,
> +			&zcd->n1, (void **)&zcd->ptr2);
> +		break;
> +	case RTE_RING_SYNC_MT:
> +	case RTE_RING_SYNC_MT_RTS:
> +	default:
> +		/* unsupported mode, shouldn't be here */
> +		RTE_ASSERT(0);
> +		n = 0;
> +		free = 0;
> +	}

Would it make sense to move __rte_ring_get_elem_addr() here and do it
only when n != 0?
I.E:

if (n != 0)
	__rte_ring_get_elem_addr(...);
	
Same comments for _dequeue_ analog.

> +
> +	if (free_space != NULL)
> +		*free_space = free - n;
> +	return n;
> +}
> +
Honnappa Nagarahalli Oct. 24, 2020, 3:45 p.m. UTC | #2
Hi Konstantin,
	Thank you for the quick comments. Please see the responses inline.

<snip>

> 
> 
> >
> > Add zero-copy APIs. These APIs provide the capability to copy the data
> > to/from the ring memory directly, without having a temporary copy (for
> > ex: an array of mbufs on the stack). Use cases that involve copying
> > large amount of data to/from the ring can benefit from these APIs.
> 
> LGTM in general.
> Few nits, see below.
> 
> >
> > Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> > Reviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
> > ---
> >  lib/librte_ring/meson.build        |   1 +
> >  lib/librte_ring/rte_ring_elem.h    |   1 +
> >  lib/librte_ring/rte_ring_peek_zc.h | 542
> > +++++++++++++++++++++++++++++
> >  3 files changed, 544 insertions(+)
> >  create mode 100644 lib/librte_ring/rte_ring_peek_zc.h
> 
> Need to update documentation: PG and RN.
> 
> >
> > diff --git a/lib/librte_ring/meson.build b/lib/librte_ring/meson.build
> > index 31c0b4649..36fdcb6a5 100644
> > --- a/lib/librte_ring/meson.build
> > +++ b/lib/librte_ring/meson.build
> > @@ -11,5 +11,6 @@ headers = files('rte_ring.h',
> >  		'rte_ring_hts_c11_mem.h',
> >  		'rte_ring_peek.h',
> >  		'rte_ring_peek_c11_mem.h',
> > +		'rte_ring_peek_zc.h',
> >  		'rte_ring_rts.h',
> >  		'rte_ring_rts_c11_mem.h')
> > diff --git a/lib/librte_ring/rte_ring_elem.h
> > b/lib/librte_ring/rte_ring_elem.h index 938b398fc..7034d29c0 100644
> > --- a/lib/librte_ring/rte_ring_elem.h
> > +++ b/lib/librte_ring/rte_ring_elem.h
> > @@ -1079,6 +1079,7 @@ rte_ring_dequeue_burst_elem(struct rte_ring *r,
> > void *obj_table,
> >
> >  #ifdef ALLOW_EXPERIMENTAL_API
> >  #include <rte_ring_peek.h>
> > +#include <rte_ring_peek_zc.h>
> >  #endif
> >
> >  #include <rte_ring.h>
> > diff --git a/lib/librte_ring/rte_ring_peek_zc.h
> > b/lib/librte_ring/rte_ring_peek_zc.h
> > new file mode 100644
> > index 000000000..9db2d343f
> > --- /dev/null
> > +++ b/lib/librte_ring/rte_ring_peek_zc.h
> > @@ -0,0 +1,542 @@
> > +/* SPDX-License-Identifier: BSD-3-Clause
> > + *
> > + * Copyright (c) 2020 Arm Limited
> > + * Copyright (c) 2007-2009 Kip Macy kmacy@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_ZC_H_
> > +#define _RTE_RING_PEEK_ZC_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 Zero Copy APIs
> > + * These APIs make it possible to split public enqueue/dequeue API
> > + * into 3 parts:
> > + * - enqueue/dequeue start
> > + * - copy data to/from the ring
> > + * - enqueue/dequeue finish
> > + * Along with the advantages of the peek APIs, these APIs provide the
> > +ability
> > + * to avoid copying of the data to temporary area (for ex: array of
> > +mbufs
> > + * on the stack).
> > + *
> > + * Note that currently these APIs are available 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 user's responsibility to create/init ring with appropriate
> > +sync
> > + * modes selected.
> > + *
> > + * Following are some examples showing the API usage.
> > + * 1)
> > + * struct elem_obj {uint64_t a; uint32_t b, c;};
> > + * struct elem_obj *obj;
> > + *
> > + * // Create ring with sync type RTE_RING_SYNC_ST or
> > +RTE_RING_SYNC_MT_HTS
> > + * // Reserve space on the ring
> > + * n = rte_ring_enqueue_zc_bulk_elem_start(r, sizeof(elem_obj), 1,
> > +&zcd, NULL);
> > + *
> > + * // Produce the data directly on the ring memory
> > + * obj = (struct elem_obj *)zcd->ptr1;
> > + * obj.a = rte_get_a();
> 
> As obj is a pointer, should be obj->a = ...
> Same for b and c.
Will fix.

> 
> > + * obj.b = rte_get_b();
> > + * obj.c = rte_get_c();
> > + * rte_ring_enqueue_zc_elem_finish(ring, n);
> > + *
> > + * 2)
> > + * // Create ring with sync type RTE_RING_SYNC_ST or
> > + RTE_RING_SYNC_MT_HTS
> > + * // Reserve space on the ring
> > + * n = rte_ring_enqueue_zc_burst_start(r, 32, &zcd, NULL);
> > + *
> > + * // Pkt I/O core polls packets from the NIC
> > + * if (n == 32)
> > + *	nb_rx = rte_eth_rx_burst(portid, queueid, zcd->ptr1, 32);
> > + * else
> > + *	nb_rx = rte_eth_rx_burst(portid, queueid, zcd->ptr1, zcd->n1);
> 
> Hmm, that doesn't look exactly correct to me.
> It could be that n == 32, but we still need to do wrap-around.
> Shouldn't it be:
> 
> If (n != 0) {
> 	nb_rx = rte_eth_rx_burst(portid, queueid, zcd->ptr1, zcd->n1);
> 	if (nb_rx == zcd->n1 && nb_rx != n)
> 		nb_rx += rte_eth_rx_burst(portid, queueid, zcd->ptr2, n -
> nb_rx); }
Agree

> 
> > + *
> > + * // Provide packets to the packet processing cores
> > + * rte_ring_enqueue_zc_finish(r, nb_rx);
> > + *
> > + * Note that between _start_ and _finish_ none other thread can
> > + proceed
> > + * with enqueue/dequeue operation till _finish_ completes.
> > + */
> > +
> > +#ifdef __cplusplus
> > +extern "C" {
> > +#endif
> > +
> > +#include <rte_ring_peek_c11_mem.h>
> > +
> > +/**
> > + * Ring zero-copy information structure.
> > + *
> > + * This structure contains the pointers and length of the space
> > + * reserved on the ring storage.
> > + */
> > +struct rte_ring_zc_data {
> > +	/* Pointer to the first space in the ring */
> > +	void **ptr1;
> 
> Why not just 'void *ptr1;'?
> Same for ptr2.
Agree

> 
> > +	/* Pointer to the second space in the ring if there is wrap-around */
> > +	void **ptr2;
> > +	/* Number of elements in the first pointer. If this is equal to
> > +	 * the number of elements requested, then ptr2 is NULL.
> > +	 * Otherwise, subtracting n1 from number of elements requested
> > +	 * will give the number of elements available at ptr2.
> > +	 */
> > +	unsigned int n1;
> > +} __rte_cache_aligned;
> > +
> > +static __rte_always_inline void
> > +__rte_ring_get_elem_addr(struct rte_ring *r, uint32_t head,
> > +	uint32_t esize, uint32_t num, void **dst1, uint32_t *n1, void
> > +**dst2) {
> > +	uint32_t idx, scale, nr_idx;
> > +	uint32_t *ring = (uint32_t *)&r[1];
> > +
> > +	/* Normalize to uint32_t */
> > +	scale = esize / sizeof(uint32_t);
> > +	idx = head & r->mask;
> > +	nr_idx = idx * scale;
> > +
> > +	*dst1 = ring + nr_idx;
> > +	*n1 = num;
> > +
> > +	if (idx + num > r->size) {
> > +		*n1 = r->size - idx;
> > +		*dst2 = ring;
> > +	}
> 
> Seems like missing:
> else {*dst2 = NULL;}
I did not add it since dst2 should be accessed only if there is wrap-around. Will call it out in the struct above.

> 
> > +}
> > +
> > +/**
> > + * @internal This function moves prod head value.
> > + */
> > +static __rte_always_inline unsigned int
> > +__rte_ring_do_enqueue_zc_elem_start(struct rte_ring *r, unsigned int
> esize,
> > +		uint32_t n, enum rte_ring_queue_behavior behavior,
> > +		struct rte_ring_zc_data *zcd, unsigned int *free_space) {
> > +	uint32_t free, head, next;
> > +
> > +	switch (r->prod.sync_type) {
> > +	case RTE_RING_SYNC_ST:
> > +		n = __rte_ring_move_prod_head(r, RTE_RING_SYNC_ST, n,
> > +			behavior, &head, &next, &free);
> > +		__rte_ring_get_elem_addr(r, head, esize, n, (void **)&zcd-
> >ptr1,
> 
> If you change ptr1, ptr2 to be just 'void *', then probably no extra type-cast
> will be needed here.
Thanks for catching this, pointers are out of whack.

> 
> > +			&zcd->n1, (void **)&zcd->ptr2);
> > +		break;
> > +	case RTE_RING_SYNC_MT_HTS:
> > +		n = __rte_ring_hts_move_prod_head(r, n, behavior, &head,
> &free);
> > +		__rte_ring_get_elem_addr(r, head, esize, n, (void **)&zcd-
> >ptr1,
> > +			&zcd->n1, (void **)&zcd->ptr2);
> > +		break;
> > +	case RTE_RING_SYNC_MT:
> > +	case RTE_RING_SYNC_MT_RTS:
> > +	default:
> > +		/* unsupported mode, shouldn't be here */
> > +		RTE_ASSERT(0);
> > +		n = 0;
> > +		free = 0;
> > +	}
> 
> Would it make sense to move __rte_ring_get_elem_addr() here and do it
> only when n != 0?
> I.E:
> 
> if (n != 0)
> 	__rte_ring_get_elem_addr(...);
It adds an 'if' statement. We can add a return to the default case and skip the if statement.

> 
> Same comments for _dequeue_ analog.
> 
> > +
> > +	if (free_space != NULL)
> > +		*free_space = free - n;
> > +	return n;
> > +}
> > +

Patch
diff mbox series

diff --git a/lib/librte_ring/meson.build b/lib/librte_ring/meson.build
index 31c0b4649..36fdcb6a5 100644
--- a/lib/librte_ring/meson.build
+++ b/lib/librte_ring/meson.build
@@ -11,5 +11,6 @@  headers = files('rte_ring.h',
 		'rte_ring_hts_c11_mem.h',
 		'rte_ring_peek.h',
 		'rte_ring_peek_c11_mem.h',
+		'rte_ring_peek_zc.h',
 		'rte_ring_rts.h',
 		'rte_ring_rts_c11_mem.h')
diff --git a/lib/librte_ring/rte_ring_elem.h b/lib/librte_ring/rte_ring_elem.h
index 938b398fc..7034d29c0 100644
--- a/lib/librte_ring/rte_ring_elem.h
+++ b/lib/librte_ring/rte_ring_elem.h
@@ -1079,6 +1079,7 @@  rte_ring_dequeue_burst_elem(struct rte_ring *r, void *obj_table,
 
 #ifdef ALLOW_EXPERIMENTAL_API
 #include <rte_ring_peek.h>
+#include <rte_ring_peek_zc.h>
 #endif
 
 #include <rte_ring.h>
diff --git a/lib/librte_ring/rte_ring_peek_zc.h b/lib/librte_ring/rte_ring_peek_zc.h
new file mode 100644
index 000000000..9db2d343f
--- /dev/null
+++ b/lib/librte_ring/rte_ring_peek_zc.h
@@ -0,0 +1,542 @@ 
+/* SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright (c) 2020 Arm Limited
+ * Copyright (c) 2007-2009 Kip Macy kmacy@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_ZC_H_
+#define _RTE_RING_PEEK_ZC_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 Zero Copy APIs
+ * These APIs make it possible to split public enqueue/dequeue API
+ * into 3 parts:
+ * - enqueue/dequeue start
+ * - copy data to/from the ring
+ * - enqueue/dequeue finish
+ * Along with the advantages of the peek APIs, these APIs provide the ability
+ * to avoid copying of the data to temporary area (for ex: array of mbufs
+ * on the stack).
+ *
+ * Note that currently these APIs are available 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 user's responsibility to create/init ring with appropriate sync
+ * modes selected.
+ *
+ * Following are some examples showing the API usage.
+ * 1)
+ * struct elem_obj {uint64_t a; uint32_t b, c;};
+ * struct elem_obj *obj;
+ *
+ * // Create ring with sync type RTE_RING_SYNC_ST or RTE_RING_SYNC_MT_HTS
+ * // Reserve space on the ring
+ * n = rte_ring_enqueue_zc_bulk_elem_start(r, sizeof(elem_obj), 1, &zcd, NULL);
+ *
+ * // Produce the data directly on the ring memory
+ * obj = (struct elem_obj *)zcd->ptr1;
+ * obj.a = rte_get_a();
+ * obj.b = rte_get_b();
+ * obj.c = rte_get_c();
+ * rte_ring_enqueue_zc_elem_finish(ring, n);
+ *
+ * 2)
+ * // Create ring with sync type RTE_RING_SYNC_ST or RTE_RING_SYNC_MT_HTS
+ * // Reserve space on the ring
+ * n = rte_ring_enqueue_zc_burst_start(r, 32, &zcd, NULL);
+ *
+ * // Pkt I/O core polls packets from the NIC
+ * if (n == 32)
+ *	nb_rx = rte_eth_rx_burst(portid, queueid, zcd->ptr1, 32);
+ * else
+ *	nb_rx = rte_eth_rx_burst(portid, queueid, zcd->ptr1, zcd->n1);
+ *
+ * // Provide packets to the packet processing cores
+ * rte_ring_enqueue_zc_finish(r, nb_rx);
+ *
+ * Note that between _start_ and _finish_ none other thread can proceed
+ * with enqueue/dequeue operation till _finish_ completes.
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <rte_ring_peek_c11_mem.h>
+
+/**
+ * Ring zero-copy information structure.
+ *
+ * This structure contains the pointers and length of the space
+ * reserved on the ring storage.
+ */
+struct rte_ring_zc_data {
+	/* Pointer to the first space in the ring */
+	void **ptr1;
+	/* Pointer to the second space in the ring if there is wrap-around */
+	void **ptr2;
+	/* Number of elements in the first pointer. If this is equal to
+	 * the number of elements requested, then ptr2 is NULL.
+	 * Otherwise, subtracting n1 from number of elements requested
+	 * will give the number of elements available at ptr2.
+	 */
+	unsigned int n1;
+} __rte_cache_aligned;
+
+static __rte_always_inline void
+__rte_ring_get_elem_addr(struct rte_ring *r, uint32_t head,
+	uint32_t esize, uint32_t num, void **dst1, uint32_t *n1, void **dst2)
+{
+	uint32_t idx, scale, nr_idx;
+	uint32_t *ring = (uint32_t *)&r[1];
+
+	/* Normalize to uint32_t */
+	scale = esize / sizeof(uint32_t);
+	idx = head & r->mask;
+	nr_idx = idx * scale;
+
+	*dst1 = ring + nr_idx;
+	*n1 = num;
+
+	if (idx + num > r->size) {
+		*n1 = r->size - idx;
+		*dst2 = ring;
+	}
+}
+
+/**
+ * @internal This function moves prod head value.
+ */
+static __rte_always_inline unsigned int
+__rte_ring_do_enqueue_zc_elem_start(struct rte_ring *r, unsigned int esize,
+		uint32_t n, enum rte_ring_queue_behavior behavior,
+		struct rte_ring_zc_data *zcd, unsigned int *free_space)
+{
+	uint32_t free, head, next;
+
+	switch (r->prod.sync_type) {
+	case RTE_RING_SYNC_ST:
+		n = __rte_ring_move_prod_head(r, RTE_RING_SYNC_ST, n,
+			behavior, &head, &next, &free);
+		__rte_ring_get_elem_addr(r, head, esize, n, (void **)&zcd->ptr1,
+			&zcd->n1, (void **)&zcd->ptr2);
+		break;
+	case RTE_RING_SYNC_MT_HTS:
+		n = __rte_ring_hts_move_prod_head(r, n, behavior, &head, &free);
+		__rte_ring_get_elem_addr(r, head, esize, n, (void **)&zcd->ptr1,
+			&zcd->n1, (void **)&zcd->ptr2);
+		break;
+	case RTE_RING_SYNC_MT:
+	case RTE_RING_SYNC_MT_RTS:
+	default:
+		/* unsupported mode, shouldn't be here */
+		RTE_ASSERT(0);
+		n = 0;
+		free = 0;
+	}
+
+	if (free_space != NULL)
+		*free_space = free - n;
+	return n;
+}
+
+/**
+ * Start to enqueue several objects on the ring.
+ * Note that no actual objects are put in the queue by this function,
+ * it just reserves space for the user on the ring.
+ * User has to copy objects into the queue using the returned pointers.
+ * User should call rte_ring_enqueue_zc_elem_finish to complete the
+ * enqueue operation.
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param esize
+ *   The size of ring element, in bytes. It must be a multiple of 4.
+ * @param n
+ *   The number of objects to add in the ring.
+ * @param zcd
+ *   Structure containing the pointers and length of the space
+ *   reserved on the ring storage.
+ * @param free_space
+ *   If non-NULL, returns the amount of space in the ring after the
+ *   reservation 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_zc_bulk_elem_start(struct rte_ring *r, unsigned int esize,
+	unsigned int n, struct rte_ring_zc_data *zcd, unsigned int *free_space)
+{
+	return __rte_ring_do_enqueue_zc_elem_start(r, esize, n,
+			RTE_RING_QUEUE_FIXED, zcd, free_space);
+}
+
+/**
+ * Start to enqueue several pointers to objects on the ring.
+ * Note that no actual pointers are put in the queue by this function,
+ * it just reserves space for the user on the ring.
+ * User has to copy pointers to objects into the queue using the
+ * returned pointers.
+ * User should call rte_ring_enqueue_zc_finish to complete the
+ * enqueue operation.
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param n
+ *   The number of objects to add in the ring.
+ * @param zcd
+ *   Structure containing the pointers and length of the space
+ *   reserved on the ring storage.
+ * @param free_space
+ *   If non-NULL, returns the amount of space in the ring after the
+ *   reservation 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_zc_bulk_start(struct rte_ring *r, unsigned int n,
+	struct rte_ring_zc_data *zcd, unsigned int *free_space)
+{
+	return rte_ring_enqueue_zc_bulk_elem_start(r, sizeof(uintptr_t), n,
+							zcd, free_space);
+}
+/**
+ * Start to enqueue several objects on the ring.
+ * Note that no actual objects are put in the queue by this function,
+ * it just reserves space for the user on the ring.
+ * User has to copy objects into the queue using the returned pointers.
+ * User should call rte_ring_enqueue_zc_elem_finish to complete the
+ * enqueue operation.
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param esize
+ *   The size of ring element, in bytes. It must be a multiple of 4.
+ * @param n
+ *   The number of objects to add in the ring.
+ * @param zcd
+ *   Structure containing the pointers and length of the space
+ *   reserved on the ring storage.
+ * @param free_space
+ *   If non-NULL, returns the amount of space in the ring after the
+ *   reservation 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_zc_burst_elem_start(struct rte_ring *r, unsigned int esize,
+	unsigned int n, struct rte_ring_zc_data *zcd, unsigned int *free_space)
+{
+	return __rte_ring_do_enqueue_zc_elem_start(r, esize, n,
+			RTE_RING_QUEUE_VARIABLE, zcd, free_space);
+}
+
+/**
+ * Start to enqueue several pointers to objects on the ring.
+ * Note that no actual pointers are put in the queue by this function,
+ * it just reserves space for the user on the ring.
+ * User has to copy pointers to objects into the queue using the
+ * returned pointers.
+ * User should call rte_ring_enqueue_zc_finish to complete the
+ * enqueue operation.
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param n
+ *   The number of objects to add in the ring.
+ * @param zcd
+ *   Structure containing the pointers and length of the space
+ *   reserved on the ring storage.
+ * @param free_space
+ *   If non-NULL, returns the amount of space in the ring after the
+ *   reservation 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_zc_burst_start(struct rte_ring *r, unsigned int n,
+	struct rte_ring_zc_data *zcd, unsigned int *free_space)
+{
+	return rte_ring_enqueue_zc_burst_elem_start(r, sizeof(uintptr_t), n,
+							zcd, free_space);
+}
+
+/**
+ * Complete enqueuing several objects on the ring.
+ * Note that number of objects to enqueue should not exceed previous
+ * enqueue_start return value.
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param n
+ *   The number of objects to add to the ring.
+ */
+__rte_experimental
+static __rte_always_inline void
+rte_ring_enqueue_zc_elem_finish(struct rte_ring *r, unsigned int n)
+{
+	uint32_t tail;
+
+	switch (r->prod.sync_type) {
+	case RTE_RING_SYNC_ST:
+		n = __rte_ring_st_get_tail(&r->prod, &tail, n);
+		__rte_ring_st_set_head_tail(&r->prod, tail, n, 1);
+		break;
+	case RTE_RING_SYNC_MT_HTS:
+		n = __rte_ring_hts_get_tail(&r->hts_prod, &tail, n);
+		__rte_ring_hts_set_head_tail(&r->hts_prod, tail, n, 1);
+		break;
+	case RTE_RING_SYNC_MT:
+	case RTE_RING_SYNC_MT_RTS:
+	default:
+		/* unsupported mode, shouldn't be here */
+		RTE_ASSERT(0);
+	}
+}
+
+/**
+ * Complete enqueuing several pointers to objects on the ring.
+ * Note that number of objects to enqueue should not exceed previous
+ * enqueue_start return value.
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param n
+ *   The number of pointers to objects to add to the ring.
+ */
+__rte_experimental
+static __rte_always_inline void
+rte_ring_enqueue_zc_finish(struct rte_ring *r, unsigned int n)
+{
+	rte_ring_enqueue_zc_elem_finish(r, n);
+}
+
+/**
+ * @internal This function moves cons head value and copies up to *n*
+ * objects from the ring to the user provided obj_table.
+ */
+static __rte_always_inline unsigned int
+__rte_ring_do_dequeue_zc_elem_start(struct rte_ring *r,
+	uint32_t esize, uint32_t n, enum rte_ring_queue_behavior behavior,
+	struct rte_ring_zc_data *zcd, unsigned int *available)
+{
+	uint32_t avail, head, next;
+
+	switch (r->cons.sync_type) {
+	case RTE_RING_SYNC_ST:
+		n = __rte_ring_move_cons_head(r, RTE_RING_SYNC_ST, n,
+			behavior, &head, &next, &avail);
+		__rte_ring_get_elem_addr(r, head, esize, n, (void **)&zcd->ptr1,
+			&zcd->n1, (void **)&zcd->ptr2);
+		break;
+	case RTE_RING_SYNC_MT_HTS:
+		n = __rte_ring_hts_move_cons_head(r, n, behavior,
+			&head, &avail);
+		__rte_ring_get_elem_addr(r, head, esize, n, (void **)&zcd->ptr1,
+			&zcd->n1, (void **)&zcd->ptr2);
+		break;
+	case RTE_RING_SYNC_MT:
+	case RTE_RING_SYNC_MT_RTS:
+	default:
+		/* unsupported mode, shouldn't be here */
+		RTE_ASSERT(0);
+		n = 0;
+		avail = 0;
+	}
+
+	if (available != NULL)
+		*available = avail - n;
+	return n;
+}
+
+/**
+ * Start to dequeue several objects from the ring.
+ * Note that no actual objects are copied from the queue by this function.
+ * User has to copy objects from the queue using the returned pointers.
+ * User should call rte_ring_dequeue_zc_elem_finish to complete the
+ * dequeue operation.
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param esize
+ *   The size of ring element, in bytes. It must be a multiple of 4.
+ * @param n
+ *   The number of objects to remove from the ring.
+ * @param zcd
+ *   Structure containing the pointers and length of the space
+ *   reserved on the ring storage.
+ * @param available
+ *   If non-NULL, returns the number of remaining ring entries after the
+ *   dequeue has finished.
+ * @return
+ *   The number of objects that can be dequeued, either 0 or n
+ */
+__rte_experimental
+static __rte_always_inline unsigned int
+rte_ring_dequeue_zc_bulk_elem_start(struct rte_ring *r, unsigned int esize,
+	unsigned int n, struct rte_ring_zc_data *zcd, unsigned int *available)
+{
+	return __rte_ring_do_dequeue_zc_elem_start(r, esize, n,
+			RTE_RING_QUEUE_FIXED, zcd, available);
+}
+
+/**
+ * Start to dequeue several pointers to objects from the ring.
+ * Note that no actual pointers are removed from the queue by this function.
+ * User has to copy pointers to objects from the queue using the
+ * returned pointers.
+ * User should call rte_ring_dequeue_zc_finish to complete the
+ * dequeue operation.
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param n
+ *   The number of objects to remove from the ring.
+ * @param zcd
+ *   Structure containing the pointers and length of the space
+ *   reserved on the ring storage.
+ * @param available
+ *   If non-NULL, returns the number of remaining ring entries after the
+ *   dequeue has finished.
+ * @return
+ *   The number of objects that can be dequeued, either 0 or n
+ */
+__rte_experimental
+static __rte_always_inline unsigned int
+rte_ring_dequeue_zc_bulk_start(struct rte_ring *r, unsigned int n,
+	struct rte_ring_zc_data *zcd, unsigned int *available)
+{
+	return rte_ring_dequeue_zc_bulk_elem_start(r, sizeof(uintptr_t),
+		n, zcd, available);
+}
+
+/**
+ * Start to dequeue several objects from the ring.
+ * Note that no actual objects are copied from the queue by this function.
+ * User has to copy objects from the queue using the returned pointers.
+ * User should call rte_ring_dequeue_zc_elem_finish to complete the
+ * dequeue operation.
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @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.
+ * @param zcd
+ *   Structure containing the pointers and length of the space
+ *   reserved on the ring storage.
+ * @param available
+ *   If non-NULL, returns the number of remaining ring entries after the
+ *   dequeue has finished.
+ * @return
+ *   The number of objects that can be dequeued, either 0 or n
+ */
+__rte_experimental
+static __rte_always_inline unsigned int
+rte_ring_dequeue_zc_burst_elem_start(struct rte_ring *r, unsigned int esize,
+	unsigned int n, struct rte_ring_zc_data *zcd, unsigned int *available)
+{
+	return __rte_ring_do_dequeue_zc_elem_start(r, esize, n,
+			RTE_RING_QUEUE_VARIABLE, zcd, available);
+}
+
+/**
+ * Start to dequeue several pointers to objects from the ring.
+ * Note that no actual pointers are removed from the queue by this function.
+ * User has to copy pointers to objects from the queue using the
+ * returned pointers.
+ * User should call rte_ring_dequeue_zc_finish to complete the
+ * dequeue operation.
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param n
+ *   The number of objects to remove from the ring.
+ * @param zcd
+ *   Structure containing the pointers and length of the space
+ *   reserved on the ring storage.
+ * @param available
+ *   If non-NULL, returns the number of remaining ring entries after the
+ *   dequeue has finished.
+ * @return
+ *   The number of objects that can be dequeued, either 0 or n
+ */
+__rte_experimental
+static __rte_always_inline unsigned int
+rte_ring_dequeue_zc_burst_start(struct rte_ring *r, unsigned int n,
+		struct rte_ring_zc_data *zcd, unsigned int *available)
+{
+	return rte_ring_dequeue_zc_burst_elem_start(r, sizeof(uintptr_t), n,
+			zcd, available);
+}
+
+/**
+ * Complete dequeuing several objects from the ring.
+ * Note that number of objects to dequeued should not exceed previous
+ * dequeue_start return value.
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param n
+ *   The number of objects to remove from the ring.
+ */
+__rte_experimental
+static __rte_always_inline void
+rte_ring_dequeue_zc_elem_finish(struct rte_ring *r, unsigned int n)
+{
+	uint32_t tail;
+
+	switch (r->cons.sync_type) {
+	case RTE_RING_SYNC_ST:
+		n = __rte_ring_st_get_tail(&r->cons, &tail, n);
+		__rte_ring_st_set_head_tail(&r->cons, tail, n, 0);
+		break;
+	case RTE_RING_SYNC_MT_HTS:
+		n = __rte_ring_hts_get_tail(&r->hts_cons, &tail, n);
+		__rte_ring_hts_set_head_tail(&r->hts_cons, tail, n, 0);
+		break;
+	case RTE_RING_SYNC_MT:
+	case RTE_RING_SYNC_MT_RTS:
+	default:
+		/* unsupported mode, shouldn't be here */
+		RTE_ASSERT(0);
+	}
+}
+
+/**
+ * Complete dequeuing several objects from the ring.
+ * Note that number of objects to dequeued should not exceed previous
+ * dequeue_start return value.
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param n
+ *   The number of objects to remove from the ring.
+ */
+__rte_experimental
+static __rte_always_inline void
+rte_ring_dequeue_zc_finish(struct rte_ring *r, unsigned int n)
+{
+	rte_ring_dequeue_elem_finish(r, n);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _RTE_RING_PEEK_ZC_H_ */