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From: Phil Yang <phil.yang@arm.com>
To: olivier.matz@6wind.com,
dev@dpdk.org
Cc: stephen@networkplumber.org, david.marchand@redhat.com,
drc@linux.vnet.ibm.com, Honnappa.Nagarahalli@arm.com, Ruifeng.Wang@arm.com,
nd@arm.com
Date: Thu, 9 Jul 2020 18:10:42 +0800
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Subject: [dpdk-dev] [PATCH v3] mbuf: use C11 atomic built-ins for refcnt
operations
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Use C11 atomic built-ins with explicit ordering instead of rte_atomic
ops which enforce unnecessary barriers on aarch64.
Signed-off-by: Phil Yang <phil.yang@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
---
v3:
1.Fix ABI breakage.
2.Simplify data type cast.
v2:
Fix ABI issue: revert the rte_mbuf_ext_shared_info struct refcnt field
to refcnt_atomic.
lib/librte_mbuf/rte_mbuf.c | 1 -
lib/librte_mbuf/rte_mbuf.h | 19 ++++++++++---------
lib/librte_mbuf/rte_mbuf_core.h | 2 +-
3 files changed, 11 insertions(+), 11 deletions(-)
diff --git a/lib/librte_mbuf/rte_mbuf.c b/lib/librte_mbuf/rte_mbuf.c
index ae91ae2..8a456e5 100644
--- a/lib/librte_mbuf/rte_mbuf.c
+++ b/lib/librte_mbuf/rte_mbuf.c
@@ -22,7 +22,6 @@
#include <rte_eal.h>
#include <rte_per_lcore.h>
#include <rte_lcore.h>
-#include <rte_atomic.h>
#include <rte_branch_prediction.h>
#include <rte_mempool.h>
#include <rte_mbuf.h>
diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
index f8e492e..c1c0956 100644
--- a/lib/librte_mbuf/rte_mbuf.h
+++ b/lib/librte_mbuf/rte_mbuf.h
@@ -37,7 +37,6 @@
#include <rte_config.h>
#include <rte_mempool.h>
#include <rte_memory.h>
-#include <rte_atomic.h>
#include <rte_prefetch.h>
#include <rte_branch_prediction.h>
#include <rte_byteorder.h>
@@ -365,7 +364,7 @@ rte_pktmbuf_priv_flags(struct rte_mempool *mp)
static inline uint16_t
rte_mbuf_refcnt_read(const struct rte_mbuf *m)
{
- return (uint16_t)(rte_atomic16_read(&m->refcnt_atomic));
+ return __atomic_load_n(&m->refcnt, __ATOMIC_RELAXED);
}
/**
@@ -378,14 +377,15 @@ rte_mbuf_refcnt_read(const struct rte_mbuf *m)
static inline void
rte_mbuf_refcnt_set(struct rte_mbuf *m, uint16_t new_value)
{
- rte_atomic16_set(&m->refcnt_atomic, (int16_t)new_value);
+ __atomic_store_n(&m->refcnt, new_value, __ATOMIC_RELAXED);
}
/* internal */
static inline uint16_t
__rte_mbuf_refcnt_update(struct rte_mbuf *m, int16_t value)
{
- return (uint16_t)(rte_atomic16_add_return(&m->refcnt_atomic, value));
+ return __atomic_add_fetch(&m->refcnt, (uint16_t)value,
+ __ATOMIC_ACQ_REL);
}
/**
@@ -466,7 +466,7 @@ rte_mbuf_refcnt_set(struct rte_mbuf *m, uint16_t new_value)
static inline uint16_t
rte_mbuf_ext_refcnt_read(const struct rte_mbuf_ext_shared_info *shinfo)
{
- return (uint16_t)(rte_atomic16_read(&shinfo->refcnt_atomic));
+ return __atomic_load_n(&shinfo->refcnt_atomic, __ATOMIC_RELAXED);
}
/**
@@ -481,7 +481,7 @@ static inline void
rte_mbuf_ext_refcnt_set(struct rte_mbuf_ext_shared_info *shinfo,
uint16_t new_value)
{
- rte_atomic16_set(&shinfo->refcnt_atomic, (int16_t)new_value);
+ __atomic_store_n(&shinfo->refcnt_atomic, new_value, __ATOMIC_RELAXED);
}
/**
@@ -505,7 +505,8 @@ rte_mbuf_ext_refcnt_update(struct rte_mbuf_ext_shared_info *shinfo,
return (uint16_t)value;
}
- return (uint16_t)rte_atomic16_add_return(&shinfo->refcnt_atomic, value);
+ return __atomic_add_fetch(&shinfo->refcnt_atomic, (uint16_t)value,
+ __ATOMIC_ACQ_REL);
}
/** Mbuf prefetch */
@@ -1304,8 +1305,8 @@ static inline int __rte_pktmbuf_pinned_extbuf_decref(struct rte_mbuf *m)
* Direct usage of add primitive to avoid
* duplication of comparing with one.
*/
- if (likely(rte_atomic16_add_return
- (&shinfo->refcnt_atomic, -1)))
+ if (likely(__atomic_add_fetch(&shinfo->refcnt_atomic, (uint16_t)-1,
+ __ATOMIC_ACQ_REL)))
return 1;
/* Reinitialize counter before mbuf freeing. */
diff --git a/lib/librte_mbuf/rte_mbuf_core.h b/lib/librte_mbuf/rte_mbuf_core.h
index 16600f1..d65d1c8 100644
--- a/lib/librte_mbuf/rte_mbuf_core.h
+++ b/lib/librte_mbuf/rte_mbuf_core.h
@@ -679,7 +679,7 @@ typedef void (*rte_mbuf_extbuf_free_callback_t)(void *addr, void *opaque);
struct rte_mbuf_ext_shared_info {
rte_mbuf_extbuf_free_callback_t free_cb; /**< Free callback function */
void *fcb_opaque; /**< Free callback argument */
- rte_atomic16_t refcnt_atomic; /**< Atomically accessed refcnt */
+ uint16_t refcnt_atomic; /**< Atomically accessed refcnt */
};
/**< Maximum number of nb_segs allowed. */
--
2.7.4