Author: bryanv
Date: Sat May 3 19:40:41 2014
New Revision: 265286
URL: http://svnweb.freebsd.org/changeset/base/265286
Log:
MFC r261150, r261151, r261164, r261166, r261167, r261168, r261394, r261395:
- Read and write the MAC address in the config space byte by byte
- Also include the mbuf's csum_flags in an assert message
- Remove stray space
- Move duplicated transmit start code into a single function
- Avoid queue unlock followed by relock when the enable interrupt race
is lost
- Check for a full virtqueue in the multiqueue transmit path
- Do not place the sglist used for Rx/Tx on the stack
- Use m_defrag() instead of m_collapse() to compact a long mbuf chain
Modified:
stable/10/sys/dev/virtio/network/if_vtnet.c
stable/10/sys/dev/virtio/network/if_vtnetvar.h
Directory Properties:
stable/10/ (props changed)
Modified: stable/10/sys/dev/virtio/network/if_vtnet.c
==============================================================================
--- stable/10/sys/dev/virtio/network/if_vtnet.c Sat May 3 18:50:47 2014
(r265285)
+++ stable/10/sys/dev/virtio/network/if_vtnet.c Sat May 3 19:40:41 2014
(r265286)
@@ -145,6 +145,7 @@ static int vtnet_txq_mq_start_locked(str
static int vtnet_txq_mq_start(struct ifnet *, struct mbuf *);
static void vtnet_txq_tq_deferred(void *, int);
#endif
+static void vtnet_txq_start(struct vtnet_txq *);
static void vtnet_txq_tq_intr(void *, int);
static void vtnet_txq_eof(struct vtnet_txq *);
static void vtnet_tx_vq_intr(void *);
@@ -606,6 +607,20 @@ vtnet_setup_features(struct vtnet_softc
} else
sc->vtnet_hdr_size = sizeof(struct virtio_net_hdr);
+ if (sc->vtnet_flags & VTNET_FLAG_MRG_RXBUFS)
+ sc->vtnet_rx_nsegs = VTNET_MRG_RX_SEGS;
+ else if (sc->vtnet_flags & VTNET_FLAG_LRO_NOMRG)
+ sc->vtnet_rx_nsegs = VTNET_MAX_RX_SEGS;
+ else
+ sc->vtnet_rx_nsegs = VTNET_MIN_RX_SEGS;
+
+ if (virtio_with_feature(dev, VIRTIO_NET_F_GSO) ||
+ virtio_with_feature(dev, VIRTIO_NET_F_HOST_TSO4) ||
+ virtio_with_feature(dev, VIRTIO_NET_F_HOST_TSO6))
+ sc->vtnet_tx_nsegs = VTNET_MAX_TX_SEGS;
+ else
+ sc->vtnet_tx_nsegs = VTNET_MIN_TX_SEGS;
+
if (virtio_with_feature(dev, VIRTIO_NET_F_CTRL_VQ)) {
sc->vtnet_flags |= VTNET_FLAG_CTRL_VQ;
@@ -661,6 +676,10 @@ vtnet_init_rxq(struct vtnet_softc *sc, i
rxq->vtnrx_sc = sc;
rxq->vtnrx_id = id;
+ rxq->vtnrx_sg = sglist_alloc(sc->vtnet_rx_nsegs, M_NOWAIT);
+ if (rxq->vtnrx_sg == NULL)
+ return (ENOMEM);
+
TASK_INIT(&rxq->vtnrx_intrtask, 0, vtnet_rxq_tq_intr, rxq);
rxq->vtnrx_tq = taskqueue_create(rxq->vtnrx_name, M_NOWAIT,
taskqueue_thread_enqueue, &rxq->vtnrx_tq);
@@ -682,6 +701,10 @@ vtnet_init_txq(struct vtnet_softc *sc, i
txq->vtntx_sc = sc;
txq->vtntx_id = id;
+ txq->vtntx_sg = sglist_alloc(sc->vtnet_tx_nsegs, M_NOWAIT);
+ if (txq->vtntx_sg == NULL)
+ return (ENOMEM);
+
#ifndef VTNET_LEGACY_TX
txq->vtntx_br = buf_ring_alloc(VTNET_DEFAULT_BUFRING_SIZE, M_DEVBUF,
M_NOWAIT, &txq->vtntx_mtx);
@@ -734,6 +757,11 @@ vtnet_destroy_rxq(struct vtnet_rxq *rxq)
rxq->vtnrx_sc = NULL;
rxq->vtnrx_id = -1;
+ if (rxq->vtnrx_sg != NULL) {
+ sglist_free(rxq->vtnrx_sg);
+ rxq->vtnrx_sg = NULL;
+ }
+
if (mtx_initialized(&rxq->vtnrx_mtx) != 0)
mtx_destroy(&rxq->vtnrx_mtx);
}
@@ -745,6 +773,11 @@ vtnet_destroy_txq(struct vtnet_txq *txq)
txq->vtntx_sc = NULL;
txq->vtntx_id = -1;
+ if (txq->vtntx_sg != NULL) {
+ sglist_free(txq->vtntx_sg);
+ txq->vtntx_sg = NULL;
+ }
+
#ifndef VTNET_LEGACY_TX
if (txq->vtntx_br != NULL) {
buf_ring_free(txq->vtntx_br, M_DEVBUF);
@@ -819,40 +852,27 @@ vtnet_alloc_virtqueues(struct vtnet_soft
struct vq_alloc_info *info;
struct vtnet_rxq *rxq;
struct vtnet_txq *txq;
- int i, idx, flags, nvqs, rxsegs, error;
+ int i, idx, flags, nvqs, error;
dev = sc->vtnet_dev;
flags = 0;
- /*
- * Indirect descriptors are not needed for the Rx virtqueue when
- * mergeable buffers are negotiated. The header is placed inline
- * with the data, not in a separate descriptor, and mbuf clusters
- * are always physically contiguous.
- */
- if (sc->vtnet_flags & VTNET_FLAG_MRG_RXBUFS)
- rxsegs = 0;
- else if (sc->vtnet_flags & VTNET_FLAG_LRO_NOMRG)
- rxsegs = VTNET_MAX_RX_SEGS;
- else
- rxsegs = VTNET_MIN_RX_SEGS;
-
nvqs = sc->vtnet_max_vq_pairs * 2;
if (sc->vtnet_flags & VTNET_FLAG_CTRL_VQ)
nvqs++;
- info = malloc(sizeof(struct vq_alloc_info) * nvqs , M_TEMP, M_NOWAIT);
+ info = malloc(sizeof(struct vq_alloc_info) * nvqs, M_TEMP, M_NOWAIT);
if (info == NULL)
return (ENOMEM);
for (i = 0, idx = 0; i < sc->vtnet_max_vq_pairs; i++, idx+=2) {
rxq = &sc->vtnet_rxqs[i];
- VQ_ALLOC_INFO_INIT(&info[idx], rxsegs,
+ VQ_ALLOC_INFO_INIT(&info[idx], sc->vtnet_rx_nsegs,
vtnet_rx_vq_intr, rxq, &rxq->vtnrx_vq,
"%s-%d rx", device_get_nameunit(dev), rxq->vtnrx_id);
txq = &sc->vtnet_txqs[i];
- VQ_ALLOC_INFO_INIT(&info[idx+1], VTNET_MAX_TX_SEGS,
+ VQ_ALLOC_INFO_INIT(&info[idx+1], sc->vtnet_tx_nsegs,
vtnet_tx_vq_intr, txq, &txq->vtntx_vq,
"%s-%d tx", device_get_nameunit(dev), txq->vtntx_id);
}
@@ -1359,14 +1379,14 @@ vtnet_rxq_replace_buf(struct vtnet_rxq *
static int
vtnet_rxq_enqueue_buf(struct vtnet_rxq *rxq, struct mbuf *m)
{
- struct sglist sg;
- struct sglist_seg segs[VTNET_MAX_RX_SEGS];
struct vtnet_softc *sc;
+ struct sglist *sg;
struct vtnet_rx_header *rxhdr;
uint8_t *mdata;
int offset, error;
sc = rxq->vtnrx_sc;
+ sg = rxq->vtnrx_sg;
mdata = mtod(m, uint8_t *);
VTNET_RXQ_LOCK_ASSERT(rxq);
@@ -1376,22 +1396,22 @@ vtnet_rxq_enqueue_buf(struct vtnet_rxq *
("%s: unexpected cluster size %d/%d", __func__, m->m_len,
sc->vtnet_rx_clsize));
- sglist_init(&sg, VTNET_MAX_RX_SEGS, segs);
+ sglist_reset(sg);
if ((sc->vtnet_flags & VTNET_FLAG_MRG_RXBUFS) == 0) {
MPASS(sc->vtnet_hdr_size == sizeof(struct virtio_net_hdr));
rxhdr = (struct vtnet_rx_header *) mdata;
- sglist_append(&sg, &rxhdr->vrh_hdr, sc->vtnet_hdr_size);
+ sglist_append(sg, &rxhdr->vrh_hdr, sc->vtnet_hdr_size);
offset = sizeof(struct vtnet_rx_header);
} else
offset = 0;
- sglist_append(&sg, mdata + offset, m->m_len - offset);
+ sglist_append(sg, mdata + offset, m->m_len - offset);
if (m->m_next != NULL) {
- error = sglist_append_mbuf(&sg, m->m_next);
+ error = sglist_append_mbuf(sg, m->m_next);
MPASS(error == 0);
}
- error = virtqueue_enqueue(rxq->vtnrx_vq, m, &sg, 0, sg.sg_nseg);
+ error = virtqueue_enqueue(rxq->vtnrx_vq, m, sg, 0, sg->sg_nseg);
return (error);
}
@@ -1818,9 +1838,9 @@ vtnet_rx_vq_intr(void *xrxq)
return;
}
-again:
VTNET_RXQ_LOCK(rxq);
+again:
if ((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0) {
VTNET_RXQ_UNLOCK(rxq);
return;
@@ -1834,10 +1854,11 @@ again:
* This is an occasional condition or race (when !more),
* so retry a few times before scheduling the taskqueue.
*/
- rxq->vtnrx_stats.vrxs_rescheduled++;
- VTNET_RXQ_UNLOCK(rxq);
if (tries++ < VTNET_INTR_DISABLE_RETRIES)
goto again;
+
+ VTNET_RXQ_UNLOCK(rxq);
+ rxq->vtnrx_stats.vrxs_rescheduled++;
taskqueue_enqueue(rxq->vtnrx_tq, &rxq->vtnrx_intrtask);
} else
VTNET_RXQ_UNLOCK(rxq);
@@ -2025,7 +2046,8 @@ vtnet_txq_offload(struct vtnet_txq *txq,
}
KASSERT(hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM,
- ("%s: mbuf %p TSO without checksum offload", __func__, m));
+ ("%s: mbuf %p TSO without checksum offload %#x",
+ __func__, m, flags));
error = vtnet_txq_offload_tso(txq, m, etype, csum_start, hdr);
if (error)
@@ -2043,45 +2065,43 @@ static int
vtnet_txq_enqueue_buf(struct vtnet_txq *txq, struct mbuf **m_head,
struct vtnet_tx_header *txhdr)
{
- struct sglist sg;
- struct sglist_seg segs[VTNET_MAX_TX_SEGS];
struct vtnet_softc *sc;
struct virtqueue *vq;
+ struct sglist *sg;
struct mbuf *m;
- int collapsed, error;
+ int error;
- vq = txq->vtntx_vq;
sc = txq->vtntx_sc;
+ vq = txq->vtntx_vq;
+ sg = txq->vtntx_sg;
m = *m_head;
- collapsed = 0;
- sglist_init(&sg, VTNET_MAX_TX_SEGS, segs);
- error = sglist_append(&sg, &txhdr->vth_uhdr, sc->vtnet_hdr_size);
- KASSERT(error == 0 && sg.sg_nseg == 1,
+ sglist_reset(sg);
+ error = sglist_append(sg, &txhdr->vth_uhdr, sc->vtnet_hdr_size);
+ KASSERT(error == 0 && sg->sg_nseg == 1,
("%s: error %d adding header to sglist", __func__, error));
-again:
- error = sglist_append_mbuf(&sg, m);
+ error = sglist_append_mbuf(sg, m);
if (error) {
- if (collapsed)
- goto fail;
-
- m = m_collapse(m, M_NOWAIT, VTNET_MAX_TX_SEGS - 1);
+ m = m_defrag(m, M_NOWAIT);
if (m == NULL)
goto fail;
*m_head = m;
- collapsed = 1;
- txq->vtntx_stats.vtxs_collapsed++;
- goto again;
+ sc->vtnet_stats.tx_defragged++;
+
+ error = sglist_append_mbuf(sg, m);
+ if (error)
+ goto fail;
}
txhdr->vth_mbuf = m;
- error = virtqueue_enqueue(vq, txhdr, &sg, sg.sg_nseg, 0);
+ error = virtqueue_enqueue(vq, txhdr, sg, sg->sg_nseg, 0);
return (error);
fail:
+ sc->vtnet_stats.tx_defrag_failed++;
m_freem(*m_head);
*m_head = NULL;
@@ -2238,6 +2258,12 @@ vtnet_txq_mq_start_locked(struct vtnet_t
vtnet_txq_eof(txq);
while ((m = drbr_peek(ifp, br)) != NULL) {
+ if (virtqueue_full(vq)) {
+ drbr_putback(ifp, br, m);
+ error = ENOBUFS;
+ break;
+ }
+
error = vtnet_txq_encap(txq, &m);
if (error) {
if (m != NULL)
@@ -2306,6 +2332,24 @@ vtnet_txq_tq_deferred(void *xtxq, int pe
#endif /* VTNET_LEGACY_TX */
static void
+vtnet_txq_start(struct vtnet_txq *txq)
+{
+ struct vtnet_softc *sc;
+ struct ifnet *ifp;
+
+ sc = txq->vtntx_sc;
+ ifp = sc->vtnet_ifp;
+
+#ifdef VTNET_LEGACY_TX
+ if (!IFQ_DRV_IS_EMPTY(&ifp->if_snd))
+ vtnet_start_locked(txq, ifp);
+#else
+ if (!drbr_empty(ifp, txq->vtntx_br))
+ vtnet_txq_mq_start_locked(txq, NULL);
+#endif
+}
+
+static void
vtnet_txq_tq_intr(void *xtxq, int pending)
{
struct vtnet_softc *sc;
@@ -2325,13 +2369,7 @@ vtnet_txq_tq_intr(void *xtxq, int pendin
vtnet_txq_eof(txq);
-#ifdef VTNET_LEGACY_TX
- if (!IFQ_DRV_IS_EMPTY(&ifp->if_snd))
- vtnet_start_locked(txq, ifp);
-#else
- if (!drbr_empty(ifp, txq->vtntx_br))
- vtnet_txq_mq_start_locked(txq, NULL);
-#endif
+ vtnet_txq_start(txq);
if (vtnet_txq_enable_intr(txq) != 0) {
vtnet_txq_disable_intr(txq);
@@ -2392,9 +2430,9 @@ vtnet_tx_vq_intr(void *xtxq)
return;
}
-again:
VTNET_TXQ_LOCK(txq);
+again:
if ((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0) {
VTNET_TXQ_UNLOCK(txq);
return;
@@ -2402,13 +2440,7 @@ again:
vtnet_txq_eof(txq);
-#ifdef VTNET_LEGACY_TX
- if (!IFQ_DRV_IS_EMPTY(&ifp->if_snd))
- vtnet_start_locked(txq, ifp);
-#else
- if (!drbr_empty(ifp, txq->vtntx_br))
- vtnet_txq_mq_start_locked(txq, NULL);
-#endif
+ vtnet_txq_start(txq);
if (vtnet_txq_enable_intr(txq) != 0) {
vtnet_txq_disable_intr(txq);
@@ -2416,9 +2448,10 @@ again:
* This is an occasional race, so retry a few times
* before scheduling the taskqueue.
*/
- VTNET_TXQ_UNLOCK(txq);
if (tries++ < VTNET_INTR_DISABLE_RETRIES)
goto again;
+
+ VTNET_TXQ_UNLOCK(txq);
txq->vtntx_stats.vtxs_rescheduled++;
taskqueue_enqueue(txq->vtntx_tq, &txq->vtntx_intrtask);
} else
@@ -2428,24 +2461,16 @@ again:
static void
vtnet_tx_start_all(struct vtnet_softc *sc)
{
- struct ifnet *ifp;
struct vtnet_txq *txq;
int i;
- ifp = sc->vtnet_ifp;
VTNET_CORE_LOCK_ASSERT(sc);
for (i = 0; i < sc->vtnet_act_vq_pairs; i++) {
txq = &sc->vtnet_txqs[i];
VTNET_TXQ_LOCK(txq);
-#ifdef VTNET_LEGACY_TX
- if (!IFQ_DRV_IS_EMPTY(&ifp->if_snd))
- vtnet_start_locked(txq, ifp);
-#else
- if (!drbr_empty(ifp, txq->vtntx_br))
- vtnet_txq_mq_start_locked(txq, NULL);
-#endif
+ vtnet_txq_start(txq);
VTNET_TXQ_UNLOCK(txq);
}
}
@@ -2521,7 +2546,6 @@ vtnet_txq_accum_stats(struct vtnet_txq *
accum->vtxs_obytes += st->vtxs_obytes;
accum->vtxs_csum += st->vtxs_csum;
accum->vtxs_tso += st->vtxs_tso;
- accum->vtxs_collapsed += st->vtxs_collapsed;
accum->vtxs_rescheduled += st->vtxs_rescheduled;
}
@@ -2839,9 +2863,10 @@ vtnet_init_rx_queues(struct vtnet_softc
sc->vtnet_rx_clsize = clsize;
sc->vtnet_rx_nmbufs = VTNET_NEEDED_RX_MBUFS(sc, clsize);
- /* The first segment is reserved for the header. */
- KASSERT(sc->vtnet_rx_nmbufs < VTNET_MAX_RX_SEGS,
- ("%s: too many rx mbufs %d", __func__, sc->vtnet_rx_nmbufs));
+ KASSERT(sc->vtnet_flags & VTNET_FLAG_MRG_RXBUFS ||
+ sc->vtnet_rx_nmbufs < sc->vtnet_rx_nsegs,
+ ("%s: too many rx mbufs %d for %d segments", __func__,
+ sc->vtnet_rx_nmbufs, sc->vtnet_rx_nsegs));
for (i = 0; i < sc->vtnet_act_vq_pairs; i++) {
rxq = &sc->vtnet_rxqs[i];
@@ -3483,6 +3508,7 @@ static void
vtnet_set_hwaddr(struct vtnet_softc *sc)
{
device_t dev;
+ int i;
dev = sc->vtnet_dev;
@@ -3490,9 +3516,11 @@ vtnet_set_hwaddr(struct vtnet_softc *sc)
if (vtnet_ctrl_mac_cmd(sc, sc->vtnet_hwaddr) != 0)
device_printf(dev, "unable to set MAC address\n");
} else if (sc->vtnet_flags & VTNET_FLAG_MAC) {
- virtio_write_device_config(dev,
- offsetof(struct virtio_net_config, mac),
- sc->vtnet_hwaddr, ETHER_ADDR_LEN);
+ for (i = 0; i < ETHER_ADDR_LEN; i++) {
+ virtio_write_dev_config_1(dev,
+ offsetof(struct virtio_net_config, mac) + i,
+ sc->vtnet_hwaddr[i]);
+ }
}
}
@@ -3500,6 +3528,7 @@ static void
vtnet_get_hwaddr(struct vtnet_softc *sc)
{
device_t dev;
+ int i;
dev = sc->vtnet_dev;
@@ -3517,8 +3546,10 @@ vtnet_get_hwaddr(struct vtnet_softc *sc)
return;
}
- virtio_read_device_config(dev, offsetof(struct virtio_net_config, mac),
- sc->vtnet_hwaddr, ETHER_ADDR_LEN);
+ for (i = 0; i < ETHER_ADDR_LEN; i++) {
+ sc->vtnet_hwaddr[i] = virtio_read_dev_config_1(dev,
+ offsetof(struct virtio_net_config, mac) + i);
+ }
}
static void
@@ -3595,8 +3626,6 @@ vtnet_setup_txq_sysctl(struct sysctl_ctx
&stats->vtxs_csum, "Transmit checksum offloaded");
SYSCTL_ADD_UQUAD(ctx, list, OID_AUTO, "tso", CTLFLAG_RD,
&stats->vtxs_tso, "Transmit segmentation offloaded");
- SYSCTL_ADD_UQUAD(ctx, list, OID_AUTO, "collapsed", CTLFLAG_RD,
- &stats->vtxs_collapsed, "Transmit mbufs collapsed");
SYSCTL_ADD_UQUAD(ctx, list, OID_AUTO, "rescheduled", CTLFLAG_RD,
&stats->vtxs_rescheduled,
"Transmit interrupt handler rescheduled");
@@ -3676,6 +3705,12 @@ vtnet_setup_stat_sysctl(struct sysctl_ct
SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "tx_tso_not_tcp",
CTLFLAG_RD, &stats->tx_tso_not_tcp,
"Aborted transmit of TSO buffer with non TCP protocol");
+ SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "tx_defragged",
+ CTLFLAG_RD, &stats->tx_defragged,
+ "Transmit mbufs defragged");
+ SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "tx_defrag_failed",
+ CTLFLAG_RD, &stats->tx_defrag_failed,
+ "Aborted transmit of buffer because defrag failed");
SYSCTL_ADD_UQUAD(ctx, child, OID_AUTO, "tx_csum_offloaded",
CTLFLAG_RD, &stats->tx_csum_offloaded,
"Offloaded checksum of transmitted buffer");
Modified: stable/10/sys/dev/virtio/network/if_vtnetvar.h
==============================================================================
--- stable/10/sys/dev/virtio/network/if_vtnetvar.h Sat May 3 18:50:47
2014 (r265285)
+++ stable/10/sys/dev/virtio/network/if_vtnetvar.h Sat May 3 19:40:41
2014 (r265286)
@@ -44,6 +44,8 @@ struct vtnet_statistics {
uint64_t tx_csum_bad_ethtype;
uint64_t tx_tso_bad_ethtype;
uint64_t tx_tso_not_tcp;
+ uint64_t tx_defragged;
+ uint64_t tx_defrag_failed;
/*
* These are accumulated from each Rx/Tx queue.
@@ -70,6 +72,7 @@ struct vtnet_rxq {
struct mtx vtnrx_mtx;
struct vtnet_softc *vtnrx_sc;
struct virtqueue *vtnrx_vq;
+ struct sglist *vtnrx_sg;
int vtnrx_id;
int vtnrx_process_limit;
struct vtnet_rxq_stats vtnrx_stats;
@@ -91,7 +94,6 @@ struct vtnet_txq_stats {
uint64_t vtxs_omcasts; /* if_omcasts */
uint64_t vtxs_csum;
uint64_t vtxs_tso;
- uint64_t vtxs_collapsed;
uint64_t vtxs_rescheduled;
};
@@ -99,6 +101,7 @@ struct vtnet_txq {
struct mtx vtntx_mtx;
struct vtnet_softc *vtntx_sc;
struct virtqueue *vtntx_vq;
+ struct sglist *vtntx_sg;
#ifndef VTNET_LEGACY_TX
struct buf_ring *vtntx_br;
#endif
@@ -143,9 +146,11 @@ struct vtnet_softc {
int vtnet_link_active;
int vtnet_hdr_size;
int vtnet_rx_process_limit;
+ int vtnet_rx_nsegs;
int vtnet_rx_nmbufs;
int vtnet_rx_clsize;
int vtnet_rx_new_clsize;
+ int vtnet_tx_nsegs;
int vtnet_if_flags;
int vtnet_act_vq_pairs;
int vtnet_max_vq_pairs;
@@ -293,11 +298,14 @@ CTASSERT(sizeof(struct vtnet_mac_filter)
/*
* Used to preallocate the Vq indirect descriptors. The first segment
- * is reserved for the header.
+ * is reserved for the header, except for mergeable buffers since the
+ * header is placed inline with the data.
*/
+#define VTNET_MRG_RX_SEGS 1
#define VTNET_MIN_RX_SEGS 2
#define VTNET_MAX_RX_SEGS 34
-#define VTNET_MAX_TX_SEGS 34
+#define VTNET_MIN_TX_SEGS 4
+#define VTNET_MAX_TX_SEGS 64
/*
* Assert we can receive and transmit the maximum with regular
@@ -314,7 +322,7 @@ CTASSERT(((VTNET_MAX_TX_SEGS - 1) * MCLB
/*
* Determine how many mbufs are in each receive buffer. For LRO without
- * mergeable descriptors, we must allocate an mbuf chain large enough to
+ * mergeable buffers, we must allocate an mbuf chain large enough to
* hold both the vtnet_rx_header and the maximum receivable data.
*/
#define VTNET_NEEDED_RX_MBUFS(_sc, _clsize) \
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