Re: [PATCH net-next] selftests: drv-net: toeplitz: cap the Rx queue count

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Jakub Kicinski wrote:
> The RPS test needs a free CPU within the first RPS_MAX_CPUS (16)
> cores. This is easily violated if the NIC or env allocates the
> IRQs to cores linearly.
> 
> Cap the Rx queues at 8, we don't need more. This makes the test
> pass on CX7 in NIPA.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Reviewed-by: Willem de Bruijn <willemb@google.com>

> ---
> CC: shuah@kernel.org
> CC: willemb@google.com
> CC: noren@nvidia.com
> CC: gal@nvidia.com
> CC: linux-kselftest@vger.kernel.org
> ---
>  .../selftests/drivers/net/hw/toeplitz.py      | 22 +++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/tools/testing/selftests/drivers/net/hw/toeplitz.py b/tools/testing/selftests/drivers/net/hw/toeplitz.py
> index cd7e080e6f84..571732198b93 100755
> --- a/tools/testing/selftests/drivers/net/hw/toeplitz.py
> +++ b/tools/testing/selftests/drivers/net/hw/toeplitz.py
> @@ -21,6 +21,8 @@ from lib.py import ksft_variants, KsftNamedVariant, KsftSkipEx, KsftFailEx
>  ETH_RSS_HASH_TOP = 1
>  # Must match RPS_MAX_CPUS in toeplitz.c
>  RPS_MAX_CPUS = 16
> +# Cap Rx queues so IRQ pinning leaves free CPUs in the RPS_MAX_CPUS range
> +QUEUE_CAP = 8
>  
>  
>  def _check_rps_and_rfs_not_configured(cfg):
> @@ -48,6 +50,25 @@ RPS_MAX_CPUS = 16
>          return int(data)
>  
>  
> +def _cap_queue_count(cfg):
> +    ehdr = {"header": {"dev-index": cfg.ifindex}}
> +    chans = cfg.ethnl.channels_get(ehdr)
> +
> +    config = {}
> +    restore = {}
> +    for key in ("combined-count", "rx-count"):

This assumes that combined and rx are not set at the same time.
SGTM, not expected in real devices. But technically they could be.

> +        cur = chans.get(key, 0)
> +        if cur > QUEUE_CAP:
> +            config[key] = QUEUE_CAP
> +            restore[key] = cur
> +
> +    if not config:
> +        return
> +
> +    cfg.ethnl.channels_set(ehdr | config)
> +    defer(cfg.ethnl.channels_set, ehdr | restore)
> +
> +
>  def _get_irq_cpus(cfg):
>      """
>      Read the list of IRQs for the device Rx queues.
> @@ -177,6 +198,7 @@ RPS_MAX_CPUS = 16
>      ]
>  
>      if grp:
> +        _cap_queue_count(cfg)
>          _check_rps_and_rfs_not_configured(cfg)
>      if grp == "rss":
>          irq_cpus = ",".join([str(x) for x in _get_irq_cpus(cfg)])
> -- 
> 2.54.0
>