Set the value of m->refcnt to 1, m->nb_segs to 1 and m->next
to NULL when the mbuf is stored inside the mempool (unused).
This is done in rte_pktmbuf_prefree_seg(), before freeing or
recycling a mbuf.
Before this patch, the value of m->refcnt was expected to be 0
while in pool.
The objectives are:
- to avoid drivers to set m->next to NULL in the early Rx path, since
this field is in the second 64B of the mbuf and its access could
trigger a cache miss
- rationalize the behavior of raw_alloc/raw_free: one is now the
symmetric of the other, and refcnt is never changed in these functions.
Signed-off-by: Olivier Matz <olivier.m...@6wind.com>
---
drivers/net/mlx5/mlx5_rxtx.c | 5 ++---
drivers/net/mpipe/mpipe_tilegx.c | 1 +
lib/librte_mbuf/rte_mbuf.c | 2 ++
lib/librte_mbuf/rte_mbuf.h | 45 +++++++++++++++++++++++++++++-----------
4 files changed, 38 insertions(+), 15 deletions(-)
diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index a518a42..294dfde 100644
--- a/drivers/net/mlx5/mlx5_rxtx.c
+++ b/drivers/net/mlx5/mlx5_rxtx.c
@@ -1327,7 +1327,8 @@ mlx5_rx_burst(void *dpdk_rxq, struct rte_mbuf **pkts,
uint16_t pkts_n)
while (pkt != seg) {
assert(pkt != (*rxq->elts)[idx]);
rep = NEXT(pkt);
- rte_mbuf_refcnt_set(pkt, 0);
+ NEXT(pkt) = NULL;
+ NB_SEGS(pkt) = 1;
rte_mbuf_raw_free(pkt);
pkt = rep;
}
@@ -1338,13 +1339,11 @@ mlx5_rx_burst(void *dpdk_rxq, struct rte_mbuf **pkts,
uint16_t pkts_n)
len = mlx5_rx_poll_len(rxq, cqe, cqe_cnt,
&rss_hash_res);
if (!len) {
- rte_mbuf_refcnt_set(rep, 0);
rte_mbuf_raw_free(rep);
break;
}
if (unlikely(len == -1)) {
/* RX error, packet is likely too large. */
- rte_mbuf_refcnt_set(rep, 0);
rte_mbuf_raw_free(rep);
++rxq->stats.idropped;
goto skip;
diff --git a/drivers/net/mpipe/mpipe_tilegx.c b/drivers/net/mpipe/mpipe_tilegx.c
index eedc0b3..560ffe9 100644
--- a/drivers/net/mpipe/mpipe_tilegx.c
+++ b/drivers/net/mpipe/mpipe_tilegx.c
@@ -548,6 +548,7 @@ mpipe_recv_flush_stack(struct mpipe_dev_priv *priv)
mbuf->packet_type = 0;
mbuf->data_len = 0;
mbuf->pkt_len = 0;
+ mbuf->next = NULL;
rte_mbuf_raw_free(mbuf);
}
diff --git a/lib/librte_mbuf/rte_mbuf.c b/lib/librte_mbuf/rte_mbuf.c
index 72ad91e..0acc810 100644
--- a/lib/librte_mbuf/rte_mbuf.c
+++ b/lib/librte_mbuf/rte_mbuf.c
@@ -145,6 +145,8 @@ rte_pktmbuf_init(struct rte_mempool *mp,
m->pool = mp;
m->nb_segs = 1;
m->port = 0xff;
+ rte_mbuf_refcnt_set(m, 1);
+ m->next = NULL;
}
/* helper to create a mbuf pool */
diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
index 8ff2290..bbd0700 100644
--- a/lib/librte_mbuf/rte_mbuf.h
+++ b/lib/librte_mbuf/rte_mbuf.h
@@ -766,6 +766,11 @@ rte_mbuf_sanity_check(const struct rte_mbuf *m, int
is_header);
* initializing all the required fields. See rte_pktmbuf_reset().
* For standard needs, prefer rte_pktmbuf_alloc().
*
+ * The caller can expect that the following fields of the mbuf structure
+ * are initialized: buf_addr, buf_physaddr, buf_len, refcnt=1, nb_segs=1,
+ * next=NULL, pool, priv_size. The other fields must be initialized
+ * by the caller.
+ *
* @param mp
* The mempool from which mbuf is allocated.
* @return
@@ -780,8 +785,9 @@ static inline struct rte_mbuf *rte_mbuf_raw_alloc(struct
rte_mempool *mp)
if (rte_mempool_get(mp, &mb) < 0)
return NULL;
m = (struct rte_mbuf *)mb;
- RTE_ASSERT(rte_mbuf_refcnt_read(m) == 0);
- rte_mbuf_refcnt_set(m, 1);
+ RTE_ASSERT(rte_mbuf_refcnt_read(m) == 1);
+ RTE_ASSERT(m->next == NULL);
+ RTE_ASSERT(m->nb_segs == 1);
__rte_mbuf_sanity_check(m, 0);
return m;
@@ -790,8 +796,13 @@ static inline struct rte_mbuf *rte_mbuf_raw_alloc(struct
rte_mempool *mp)
/**
* Put mbuf back into its original mempool.
*
- * The caller must ensure that the mbuf is direct and that the
- * reference counter is 0.
+ * The caller must ensure that the mbuf is direct and properly
+ * reinitialized (refcnt=1, next=NULL, nb_segs=1), as done by
+ * rte_pktmbuf_prefree_seg().
+ *
+ * This function should be used with care, when optimization is
+ * required. For standard needs, prefer rte_pktmbuf_free() or
+ * rte_pktmbuf_free_seg().
*
* @param m
* The mbuf to be freed.
@@ -800,13 +811,16 @@ static inline void __attribute__((always_inline))
rte_mbuf_raw_free(struct rte_mbuf *m)
{
RTE_ASSERT(RTE_MBUF_DIRECT(m));
- RTE_ASSERT(rte_mbuf_refcnt_read(m) == 0);
+ RTE_ASSERT(rte_mbuf_refcnt_read(m) == 1);
+ RTE_ASSERT(m->next == NULL);
+ RTE_ASSERT(m->nb_segs == 1);
+ __rte_mbuf_sanity_check(m, 0);
rte_mempool_put(m->pool, m);
}
/* compat with older versions */
__rte_deprecated
-static inline void __attribute__((always_inline))
+static inline void
__rte_mbuf_raw_free(struct rte_mbuf *m)
{
rte_mbuf_raw_free(m);
@@ -1218,8 +1232,12 @@ static inline void rte_pktmbuf_detach(struct rte_mbuf *m)
m->data_len = 0;
m->ol_flags = 0;
- if (rte_mbuf_refcnt_update(md, -1) == 0)
+ if (rte_mbuf_refcnt_update(md, -1) == 0) {
+ md->next = NULL;
+ md->nb_segs = 1;
+ rte_mbuf_refcnt_set(md, 1);
rte_mbuf_raw_free(md);
+ }
}
/**
@@ -1243,9 +1261,14 @@ rte_pktmbuf_prefree_seg(struct rte_mbuf *m)
__rte_mbuf_sanity_check(m, 0);
if (likely(rte_mbuf_refcnt_update(m, -1) == 0)) {
- /* if this is an indirect mbuf, it is detached. */
- if (RTE_MBUF_INDIRECT(m))
+ if (RTE_MBUF_INDIRECT(m)) {
rte_pktmbuf_detach(m);
+ /* next, nb_segs, refcnt are reset */
+ } else {
+ m->next = NULL;
+ m->nb_segs = 1;
+ rte_mbuf_refcnt_set(m, 1);
+ }
return m;
}
return NULL;
@@ -1272,10 +1295,8 @@ static inline void __attribute__((always_inline))
rte_pktmbuf_free_seg(struct rte_mbuf *m)
{
m = rte_pktmbuf_prefree_seg(m);
- if (likely(m != NULL)) {
- m->next = NULL;
+ if (likely(m != NULL))
rte_mbuf_raw_free(m);
- }
}
/**
--
2.8.1
