Hello,
On 28/09/2021 05:21, Wang, Haiyue wrote:
-----Original Message-----
From: Wang, Haiyue
Sent: Tuesday, September 28, 2021 11:06
To: 'Julien Meunier' <julien.meun...@nokia.com>; dev@dpdk.org
Cc: sta...@dpdk.org; Richardson, Bruce <bruce.richard...@intel.com>
Subject: RE: [PATCH] net/ixgbe: fix RxQ/TxQ release
-----Original Message-----
From: Julien Meunier <julien.meun...@nokia.com>
Sent: Tuesday, September 28, 2021 01:18
To: dev@dpdk.org
Cc: sta...@dpdk.org; Richardson, Bruce <bruce.richard...@intel.com>; Wang,
Haiyue
<haiyue.w...@intel.com>
Subject: [PATCH] net/ixgbe: fix RxQ/TxQ release
On the vector implementation, during the tear-down, the mbufs not
drained in the RxQ and TxQ are freed based on an algorithm which
supposed that the number of descriptors is a power of 2 (max_desc).
Based on this hypothesis, this algorithm uses a bitmask in order to
detect an index overflow during the iteration, and to restart the loop
from 0.
However, there is no such power of 2 requirement in the ixgbe for the
number of descriptors in the RxQ / TxQ. The only requirement is to have
a number correctly aligned.
If a user requested to configure a number of descriptors which is not a
power of 2, as a consequence, during the tear-down, it was possible to
be in an infinite loop, and to never reach the exit loop condition.
Are you able to setup not a power of 2 successfully ?
My fault, yes, possible. ;-)
Yes, we have some usecases where the nb of descriptiors for the TxQ is
set to 1536.
I modified the test_pmd_perf in order to validate this behavior, as my
ixgbe X550 supports the loopback mode:
- nb_desc = 2048 => txq is drained and stopped correctly
- nb_desc = 1536 => freeze during the teardown
int
rte_eth_tx_queue_setup(uint16_t port_id, uint16_t tx_queue_id,
uint16_t nb_tx_desc, unsigned int socket_id,
const struct rte_eth_txconf *tx_conf)
{
...
if (nb_tx_desc > dev_info.tx_desc_lim.nb_max ||
nb_tx_desc < dev_info.tx_desc_lim.nb_min ||
nb_tx_desc % dev_info.tx_desc_lim.nb_align != 0) {
RTE_ETHDEV_LOG(ERR,
"Invalid value for nb_tx_desc(=%hu), should be: <= %hu,
>= %hu, and a product
of %hu\n",
nb_tx_desc, dev_info.tx_desc_lim.nb_max,
dev_info.tx_desc_lim.nb_min,
dev_info.tx_desc_lim.nb_align);
return -EINVAL;
}
...
}
By removing the bitmask and changing the loop method, we can avoid this
issue, and allow the user to configure a RxQ / TxQ which is not a power
of 2.
Fixes: c95584dc2b18 ("ixgbe: new vectorized functions for Rx/Tx")
Cc: bruce.richard...@intel.com
Cc: sta...@dpdk.org
Signed-off-by: Julien Meunier <julien.meun...@nokia.com>
---
drivers/net/ixgbe/ixgbe_rxtx_vec_common.h | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
diff --git a/drivers/net/ixgbe/ixgbe_rxtx_vec_common.h
b/drivers/net/ixgbe/ixgbe_rxtx_vec_common.h
index adba855ca3..8912558918 100644
--- a/drivers/net/ixgbe/ixgbe_rxtx_vec_common.h
+++ b/drivers/net/ixgbe/ixgbe_rxtx_vec_common.h
@@ -150,11 +150,14 @@ _ixgbe_tx_queue_release_mbufs_vec(struct ixgbe_tx_queue
*txq)
return;
Just one line ?
i = (i + 1) % txq->nb_tx_desc
Ah yes, I was too focused with this bitmask...
The shorter, the better.
I will send a V2 today.
Thanks for this feedback !
/* release the used mbufs in sw_ring */
- for (i = txq->tx_next_dd - (txq->tx_rs_thresh - 1);
- i != txq->tx_tail;
- i = (i + 1) & max_desc) {
+ i = txq->tx_next_dd - (txq->tx_rs_thresh - 1);
+ while (i != txq->tx_tail) {
txe = &txq->sw_ring_v[i];
rte_pktmbuf_free_seg(txe->mbuf);
+
+ i = i + 1;
+ if (i > max_desc)
+ i = 0;
}
txq->nb_tx_free = max_desc;
@@ -168,7 +171,7 @@ _ixgbe_tx_queue_release_mbufs_vec(struct ixgbe_tx_queue
*txq)
static inline void
_ixgbe_rx_queue_release_mbufs_vec(struct ixgbe_rx_queue *rxq)
{
- const unsigned int mask = rxq->nb_rx_desc - 1;
+ const unsigned int max_desc = rxq->nb_rx_desc - 1;
unsigned int i;
if (rxq->sw_ring == NULL || rxq->rxrearm_nb >= rxq->nb_rx_desc)
@@ -181,11 +184,14 @@ _ixgbe_rx_queue_release_mbufs_vec(struct ixgbe_rx_queue
*rxq)
rte_pktmbuf_free_seg(rxq->sw_ring[i].mbuf);
}
} else {
- for (i = rxq->rx_tail;
- i != rxq->rxrearm_start;
- i = (i + 1) & mask) {
+ i = rxq->rx_tail;
+ while (i != rxq->rxrearm_start) {
if (rxq->sw_ring[i].mbuf != NULL)
rte_pktmbuf_free_seg(rxq->sw_ring[i].mbuf);
+
+ i = i + 1;
+ if (i > max_desc)
+ i = 0;
}
}
--
2.17.1
--
Julien Meunier
