Re: [PATCH 3/4] net/bonding: another fix to LACP mempool size

[Olivier MATZ <olivier.matz@6wind.com>]

Hi Robert,

On 08/01/2016 10:42 PM, Robert Sanford wrote:
> The following log message may appear after a slave is idle (or nearly
> idle) for a few minutes: "PMD: Failed to allocate LACP packet from
> pool".
>
> Problem: All mbufs from a slave's private pool (used exclusively for
> transmitting LACPDUs) have been allocated and are still sitting in
> the device's tx descriptor ring and other cores' mempool caches.
>
> Solution: Ensure that each slaves' tx (LACPDU) mempool owns more than
> n-tx-queues * (n-tx-descriptors + per-core-mempool-flush-threshold)
> mbufs.
>
> Note that the LACP tx machine function is the only code that allocates
> from a slave's private pool. It runs in the context of the interrupt
> thread, and thus it has no mempool cache of its own.
>
> Signed-off-by: Robert Sanford <rsanford@akamai.com>
> ---
>   drivers/net/bonding/rte_eth_bond_8023ad.c |   10 +++++++---
>   1 files changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/bonding/rte_eth_bond_8023ad.c b/drivers/net/bonding/rte_eth_bond_8023ad.c
> index 2f7ae70..1207896 100644
> --- a/drivers/net/bonding/rte_eth_bond_8023ad.c
> +++ b/drivers/net/bonding/rte_eth_bond_8023ad.c
> @@ -854,6 +854,8 @@ bond_mode_8023ad_activate_slave(struct rte_eth_dev *bond_dev, uint8_t slave_id)
>   	char mem_name[RTE_ETH_NAME_MAX_LEN];
>   	int socket_id;
>   	unsigned element_size;
> +	unsigned cache_size;
> +	unsigned cache_flushthresh;
>   	uint32_t total_tx_desc;
>   	struct bond_tx_queue *bd_tx_q;
>   	uint16_t q_id;
> @@ -890,19 +892,21 @@ bond_mode_8023ad_activate_slave(struct rte_eth_dev *bond_dev, uint8_t slave_id)
>
>   	element_size = sizeof(struct slow_protocol_frame) + sizeof(struct rte_mbuf)
>   				+ RTE_PKTMBUF_HEADROOM;
> +	cache_size = RTE_MEMPOOL_CACHE_MAX_SIZE >= 32 ?
> +		32 : RTE_MEMPOOL_CACHE_MAX_SIZE;
> +	cache_flushthresh = RTE_MEMPOOL_CALC_CACHE_FLUSHTHRESH(cache_size);
>
>   	/* The size of the mempool should be at least:
>   	 * the sum of the TX descriptors + BOND_MODE_8023AX_SLAVE_TX_PKTS */
>   	total_tx_desc = BOND_MODE_8023AX_SLAVE_TX_PKTS;
>   	for (q_id = 0; q_id < bond_dev->data->nb_tx_queues; q_id++) {
>   		bd_tx_q = (struct bond_tx_queue*)bond_dev->data->tx_queues[q_id];
> -		total_tx_desc += bd_tx_q->nb_tx_desc;
> +		total_tx_desc += bd_tx_q->nb_tx_desc + cache_flushthresh;
>   	}
>
>   	snprintf(mem_name, RTE_DIM(mem_name), "slave_port%u_pool", slave_id);
>   	port->mbuf_pool = rte_mempool_create(mem_name,
> -		total_tx_desc, element_size,
> -		RTE_MEMPOOL_CACHE_MAX_SIZE >= 32 ? 32 : RTE_MEMPOOL_CACHE_MAX_SIZE,
> +		total_tx_desc, element_size, cache_size,
>   		sizeof(struct rte_pktmbuf_pool_private), rte_pktmbuf_pool_init,
>   		NULL, rte_pktmbuf_init, NULL, socket_id, MEMPOOL_F_NO_SPREAD);
>
>

I'm not very familiar with bonding code, so maybe your patch is correct. 
I think the size of the mempool should be:

   BOND_MODE_8023AX_SLAVE_TX_PKTS +
     n_cores * RTE_MEMPOOL_CALC_CACHE_FLUSHTHRESH(cache_size)

With n_cores = number of cores that can dequeue from the mempool.

The safest thing to do would be to have n_cores = RTE_MAX_LCORE. I don't 
know if bond_dev->data->nb_tx_queue corresponds to this definition, if 
yes you can ignore my comment ;)


Regards,
Olivier