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From: =?UTF-8?q?Morten=20Br=C3=B8rup?= <mb@smartsharesystems.com>
To: olivier.matz@6wind.com, konstantin.ananyev@intel.com,
Honnappa.Nagarahalli@arm.com, nd@arm.com
Cc: dev@dpdk.org, =?UTF-8?q?Morten=20Br=C3=B8rup?= <mb@smartsharesystems.com>
Date: Wed, 13 May 2020 15:35:50 +0000
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Subject: [dpdk-dev] [PATCH] ring: empty and count optimizations
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Testing if the ring is empty is as simple as comparing the producer and
consumer pointers.
In theory, this optimization reduces the number of potential cache misses
from 3 to 2 by not having to read r->mask in rte_ring_count().
It is not possible to enqueue more elements than the capacity of a ring,
so the capacity comparison is a safeguard for observer threads only.
Instead of completely removing the comparison, I have reorganized it to
resemble the other trigrahps in the ring library and added a likely().
The modification of these two functions were discussed in the RFC here:
https://mails.dpdk.org/archives/dev/2020-April/165752.html
Signed-off-by: Morten Brørup <mb@smartsharesystems.com>
---
lib/librte_ring/rte_ring.h | 36 +++++++++++++++++++-----------------
1 file changed, 19 insertions(+), 17 deletions(-)
diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h
index 86faede81..74a8fcdc8 100644
--- a/lib/librte_ring/rte_ring.h
+++ b/lib/librte_ring/rte_ring.h
@@ -55,7 +55,7 @@ extern "C" {
* - The memory size needed for the ring on success.
* - -EINVAL if count is not a power of 2.
*/
-ssize_t rte_ring_get_memsize(unsigned count);
+ssize_t rte_ring_get_memsize(unsigned int count);
/**
* Initialize a ring structure.
@@ -109,8 +109,8 @@ ssize_t rte_ring_get_memsize(unsigned count);
* @return
* 0 on success, or a negative value on error.
*/
-int rte_ring_init(struct rte_ring *r, const char *name, unsigned count,
- unsigned flags);
+int rte_ring_init(struct rte_ring *r, const char *name, unsigned int count,
+ unsigned int flags);
/**
* Create a new ring named *name* in memory.
@@ -169,8 +169,8 @@ int rte_ring_init(struct rte_ring *r, const char *name, unsigned count,
* - EEXIST - a memzone with the same name already exists
* - ENOMEM - no appropriate memory area found in which to create memzone
*/
-struct rte_ring *rte_ring_create(const char *name, unsigned count,
- int socket_id, unsigned flags);
+struct rte_ring *rte_ring_create(const char *name, unsigned int count,
+ int socket_id, unsigned int flags);
/**
* De-allocate all memory used by the ring.
@@ -199,7 +199,7 @@ void rte_ring_dump(FILE *f, const struct rte_ring *r);
uint32_t idx = prod_head & (r)->mask; \
obj_type *ring = (obj_type *)ring_start; \
if (likely(idx + n < size)) { \
- for (i = 0; i < (n & ((~(unsigned)0x3))); i+=4, idx+=4) { \
+ for (i = 0; i < (n & ((~(unsigned int)0x3))); i+=4, idx+=4) { \
ring[idx] = obj_table[i]; \
ring[idx+1] = obj_table[i+1]; \
ring[idx+2] = obj_table[i+2]; \
@@ -230,7 +230,7 @@ void rte_ring_dump(FILE *f, const struct rte_ring *r);
const uint32_t size = (r)->size; \
obj_type *ring = (obj_type *)ring_start; \
if (likely(idx + n < size)) { \
- for (i = 0; i < (n & (~(unsigned)0x3)); i+=4, idx+=4) {\
+ for (i = 0; i < (n & (~(unsigned int)0x3)); i+=4, idx+=4) {\
obj_table[i] = ring[idx]; \
obj_table[i+1] = ring[idx+1]; \
obj_table[i+2] = ring[idx+2]; \
@@ -683,13 +683,13 @@ rte_ring_reset(struct rte_ring *r);
* @return
* The number of entries in the ring.
*/
-static inline unsigned
+static inline unsigned int
rte_ring_count(const struct rte_ring *r)
{
uint32_t prod_tail = r->prod.tail;
uint32_t cons_tail = r->cons.tail;
uint32_t count = (prod_tail - cons_tail) & r->mask;
- return (count > r->capacity) ? r->capacity : count;
+ return likely(count <= r->capacity) ? count : r->capacity;
}
/**
@@ -700,7 +700,7 @@ rte_ring_count(const struct rte_ring *r)
* @return
* The number of free entries in the ring.
*/
-static inline unsigned
+static inline unsigned int
rte_ring_free_count(const struct rte_ring *r)
{
return r->capacity - rte_ring_count(r);
@@ -733,7 +733,9 @@ rte_ring_full(const struct rte_ring *r)
static inline int
rte_ring_empty(const struct rte_ring *r)
{
- return rte_ring_count(r) == 0;
+ uint32_t prod_tail = r->prod.tail;
+ uint32_t cons_tail = r->cons.tail;
+ return cons_tail == prod_tail;
}
/**
@@ -860,7 +862,7 @@ struct rte_ring *rte_ring_lookup(const char *name);
* @return
* - n: Actual number of objects enqueued.
*/
-static __rte_always_inline unsigned
+static __rte_always_inline unsigned int
rte_ring_mp_enqueue_burst(struct rte_ring *r, void * const *obj_table,
unsigned int n, unsigned int *free_space)
{
@@ -883,7 +885,7 @@ rte_ring_mp_enqueue_burst(struct rte_ring *r, void * const *obj_table,
* @return
* - n: Actual number of objects enqueued.
*/
-static __rte_always_inline unsigned
+static __rte_always_inline unsigned int
rte_ring_sp_enqueue_burst(struct rte_ring *r, void * const *obj_table,
unsigned int n, unsigned int *free_space)
{
@@ -910,7 +912,7 @@ rte_ring_sp_enqueue_burst(struct rte_ring *r, void * const *obj_table,
* @return
* - n: Actual number of objects enqueued.
*/
-static __rte_always_inline unsigned
+static __rte_always_inline unsigned int
rte_ring_enqueue_burst(struct rte_ring *r, void * const *obj_table,
unsigned int n, unsigned int *free_space)
{
@@ -954,7 +956,7 @@ rte_ring_enqueue_burst(struct rte_ring *r, void * const *obj_table,
* @return
* - n: Actual number of objects dequeued, 0 if ring is empty
*/
-static __rte_always_inline unsigned
+static __rte_always_inline unsigned int
rte_ring_mc_dequeue_burst(struct rte_ring *r, void **obj_table,
unsigned int n, unsigned int *available)
{
@@ -979,7 +981,7 @@ rte_ring_mc_dequeue_burst(struct rte_ring *r, void **obj_table,
* @return
* - n: Actual number of objects dequeued, 0 if ring is empty
*/
-static __rte_always_inline unsigned
+static __rte_always_inline unsigned int
rte_ring_sc_dequeue_burst(struct rte_ring *r, void **obj_table,
unsigned int n, unsigned int *available)
{
@@ -1006,7 +1008,7 @@ rte_ring_sc_dequeue_burst(struct rte_ring *r, void **obj_table,
* @return
* - Number of objects dequeued
*/
-static __rte_always_inline unsigned
+static __rte_always_inline unsigned int
rte_ring_dequeue_burst(struct rte_ring *r, void **obj_table,
unsigned int n, unsigned int *available)
{
--
2.17.1