[PATCH net-next 06/16] idpf: a use saner limit for default number of queues to allocate

Alexander Lobakin
2025-03-05T16:22:41Z

Currently, the maximum number of queues available for one vport is 16.
This is hardcoded, but then the function calculating the optimal number
of queues takes min(16, num_online_cpus()).
On order to be able to allocate more queues, which will be then used for
XDP, stop hardcoding 16 and rely on what the device gives us. Instead of
num_online_cpus(), which is considered suboptimal since at least 2013,
use netif_get_num_default_rss_queues() to still have free queues in the
pool.
nr_cpu_ids number of Tx queues are needed only for lockless XDP sending,
the regular stack doesn't benefit from that anyhow.
On a 128-thread Xeon, this now gives me 32 regular Tx queues and leaves
224 free for XDP (128 of which will handle XDP_TX, .ndo_xdp_xmit(), and
XSk xmit when enabled).

Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
---
drivers/net/ethernet/intel/idpf/idpf_txrx.c | 8 +-------
drivers/net/ethernet/intel/idpf/idpf_virtchnl.c | 2 +-
2 files changed, 2 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/intel/idpf/idpf_txrx.c b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
index c15833928ea1..2f221c0abad8 100644
--- a/drivers/net/ethernet/intel/idpf/idpf_txrx.c
+++ b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
@@ -1234,13 +1234,7 @@ int idpf_vport_calc_total_qs(struct idpf_adapter *adapter, u16 vport_idx,
num_req_tx_qs = vport_config->user_config.num_req_tx_qs;
num_req_rx_qs = vport_config->user_config.num_req_rx_qs;
} else {
- int num_cpus;
-
- /* Restrict num of queues to cpus online as a default
- * configuration to give best performance. User can always
- * override to a max number of queues via ethtool.
- */
- num_cpus = num_online_cpus();
+ u32 num_cpus = netif_get_num_default_rss_queues();

dflt_splitq_txq_grps = min_t(int, max_q->max_txq, num_cpus);
dflt_singleq_txqs = min_t(int, max_q->max_txq, num_cpus);
diff --git a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
index 3d2413b8684f..135af3cc243f 100644
--- a/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
+++ b/drivers/net/ethernet/intel/idpf/idpf_virtchnl.c
@@ -937,7 +937,7 @@ int idpf_vport_alloc_max_qs(struct idpf_adapter *adapter,
max_tx_q = le16_to_cpu(caps->max_tx_q) / default_vports;
if (adapter->num_alloc_vports < default_vports) {
max_q->max_rxq = min_t(u16, max_rx_q, IDPF_MAX_Q);
- max_q->max_txq = min_t(u16, max_tx_q, IDPF_MAX_Q);
+ max_q->max_txq = min_t(u16, max_tx_q, IDPF_LARGE_MAX_Q);
} else {
max_q->max_rxq = IDPF_MIN_Q;
max_q->max_txq = IDPF_MIN_Q;
--
2.48.1