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netdev-dpdk: Enable tx-retries-max config.

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vhost tx retries can provide some mitigation against
dropped packets due to a temporarily slow guest/limited queue
size for an interface, but on the other hand when a system
is fully loaded those extra cycles retrying could mean
packets are dropped elsewhere.

Up to now max vhost tx retries have been hardcoded, which meant
no tuning and no way to disable for debugging to see if extra
cycles spent retrying resulted in rx drops on some other
interface.

Add an option to change the max retries, with a value of
0 effectively disabling vhost tx retries.

Signed-off-by: Kevin Traynor <ktraynor@redhat.com>
Acked-by: Eelco Chaudron <echaudro@redhat.com>
Acked-by: Flavio Leitner <fbl@sysclose.org>
Acked-by: Ilya Maximets <i.maximets@samsung.com>
Signed-off-by: Ian Stokes <ian.stokes@intel.com>
This commit is contained in:
Kevin Traynor
2019-07-02 01:32:30 +01:00
committed by Ian Stokes
parent c161357d5d
commit 080f080c3b
4 changed files with 78 additions and 4 deletions
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40
lib/netdev-dpdk.c
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@@ -164,7 +164,13 @@ BUILD_ASSERT_DECL((MAX_NB_MBUF / ROUND_DOWN_POW2(MAX_NB_MBUF / MIN_NB_MBUF))
typedef uint16_t dpdk_port_t;
#define DPDK_PORT_ID_FMT "%"PRIu16
#define VHOST_ENQ_RETRY_NUM 8
/* Minimum amount of vhost tx retries, effectively a disable. */
#define VHOST_ENQ_RETRY_MIN 0
/* Maximum amount of vhost tx retries. */
#define VHOST_ENQ_RETRY_MAX 32
/* Legacy default value for vhost tx retries. */
#define VHOST_ENQ_RETRY_DEF 8
#define IF_NAME_SZ (PATH_MAX > IFNAMSIZ ? PATH_MAX : IFNAMSIZ)
static const struct rte_eth_conf port_conf = {
@@ -417,7 +423,9 @@ struct netdev_dpdk {
/* True if vHost device is 'up' and has been reconfigured at least once */
bool vhost_reconfigured;
/* 3 pad bytes here. */
atomic_uint8_t vhost_tx_retries_max;
/* 2 pad bytes here. */
);
PADDED_MEMBERS(CACHE_LINE_SIZE,
@@ -1261,6 +1269,8 @@ vhost_common_construct(struct netdev *netdev)
return ENOMEM;
}
atomic_init(&dev->vhost_tx_retries_max, VHOST_ENQ_RETRY_DEF);
return common_construct(netdev, DPDK_ETH_PORT_ID_INVALID,
DPDK_DEV_VHOST, socket_id);
}
@@ -1921,6 +1931,7 @@ netdev_dpdk_vhost_client_set_config(struct netdev *netdev,
{
struct netdev_dpdk *dev = netdev_dpdk_cast(netdev);
const char *path;
int max_tx_retries, cur_max_tx_retries;
ovs_mutex_lock(&dev->mutex);
if (!(dev->vhost_driver_flags & RTE_VHOST_USER_CLIENT)) {
@@ -1937,6 +1948,19 @@ netdev_dpdk_vhost_client_set_config(struct netdev *netdev,
netdev_request_reconfigure(netdev);
}
}
max_tx_retries = smap_get_int(args, "tx-retries-max",
VHOST_ENQ_RETRY_DEF);
if (max_tx_retries < VHOST_ENQ_RETRY_MIN
|| max_tx_retries > VHOST_ENQ_RETRY_MAX) {
max_tx_retries = VHOST_ENQ_RETRY_DEF;
}
atomic_read_relaxed(&dev->vhost_tx_retries_max, &cur_max_tx_retries);
if (max_tx_retries != cur_max_tx_retries) {
atomic_store_relaxed(&dev->vhost_tx_retries_max, max_tx_retries);
VLOG_INFO("Max Tx retries for vhost device '%s' set to %d",
netdev_get_name(netdev), max_tx_retries);
}
ovs_mutex_unlock(&dev->mutex);
return 0;
@@ -2350,6 +2374,7 @@ __netdev_dpdk_vhost_send(struct netdev *netdev, int qid,
unsigned int total_pkts = cnt;
unsigned int dropped = 0;
int i, retries = 0;
int max_retries = VHOST_ENQ_RETRY_MIN;
int vid = netdev_dpdk_get_vid(dev);
qid = dev->tx_q[qid % netdev->n_txq].map;
@@ -2379,18 +2404,25 @@ __netdev_dpdk_vhost_send(struct netdev *netdev, int qid,
cnt -= tx_pkts;
/* Prepare for possible retry.*/
cur_pkts = &cur_pkts[tx_pkts];
if (OVS_UNLIKELY(cnt && !retries)) {
/*
* Read max retries as there are packets not sent
* and no retries have already occurred.
*/
atomic_read_relaxed(&dev->vhost_tx_retries_max, &max_retries);
}
} else {
/* No packets sent - do not retry.*/
break;
}
} while (cnt && (retries++ < VHOST_ENQ_RETRY_NUM));
} while (cnt && (retries++ < max_retries));
rte_spinlock_unlock(&dev->tx_q[qid].tx_lock);
rte_spinlock_lock(&dev->stats_lock);
netdev_dpdk_vhost_update_tx_counters(&dev->stats, pkts, total_pkts,
cnt + dropped);
dev->tx_retries += MIN(retries, VHOST_ENQ_RETRY_NUM);
dev->tx_retries += MIN(retries, max_retries);
rte_spinlock_unlock(&dev->stats_lock);
out: