[PATCH net-next] sfc: reduce the number of requested xdp ev queues

Ivan Babrou
2020-12-15T01:30:05Z

Without this change the driver tries to allocate too many queues,
breaching the number of available msi-x interrupts on machines
with many logical cpus and default adapter settings:

Insufficient resources for 12 XDP event queues (24 other channels, max 32)

Which in turn triggers EINVAL on XDP processing:

sfc 0000:86:00.0 ext0: XDP TX failed (-22)

Signed-off-by: Ivan Babrou <ivan@cloudflare.com>
---
drivers/net/ethernet/sfc/efx_channels.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/sfc/efx_channels.c b/drivers/net/ethernet/sfc/efx_channels.c
index a4a626e9cd9a..1bfeee283ea9 100644
--- a/drivers/net/ethernet/sfc/efx_channels.c
+++ b/drivers/net/ethernet/sfc/efx_channels.c
@@ -17,6 +17,7 @@
#include "rx_common.h"
#include "nic.h"
#include "sriov.h"
+#include "workarounds.h"

/* This is the first interrupt mode to try out of:
* 0 => MSI-X
@@ -137,6 +138,7 @@ static int efx_allocate_msix_channels(struct efx_nic *efx,
{
unsigned int n_channels = parallelism;
int vec_count;
+ int tx_per_ev;
int n_xdp_tx;
int n_xdp_ev;

@@ -149,9 +151,9 @@ static int efx_allocate_msix_channels(struct efx_nic *efx,
* multiple tx queues, assuming tx and ev queues are both
* maximum size.
*/
-
+ tx_per_ev = EFX_MAX_EVQ_SIZE / EFX_TXQ_MAX_ENT(efx);
n_xdp_tx = num_possible_cpus();
- n_xdp_ev = DIV_ROUND_UP(n_xdp_tx, EFX_MAX_TXQ_PER_CHANNEL);
+ n_xdp_ev = DIV_ROUND_UP(n_xdp_tx, tx_per_ev);

vec_count = pci_msix_vec_count(efx->pci_dev);
if (vec_count < 0)
--
2.29.2