Re: [PATCH] net/gve: Change ERR to DEBUG to prevent flooding of logs for Tx-Dqo.

[Ferruh Yigit <ferruh.yigit@amd.com>]

On 2/19/2024 2:44 AM, Rushil Gupta wrote:
> This was causing failure for testpmd runs (for queues >=15)
> presumably due to flooding of logs due to descriptor ring being
> overwritten.
> 
> Fixes: a01854 ("net/gve: fix dqo bug for chained descriptors")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Rushil Gupta <rushilg@google.com>
> Reviewed-by: Joshua Washington <joshwash@google.com>
> ---
>  drivers/net/gve/gve_tx_dqo.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/gve/gve_tx_dqo.c b/drivers/net/gve/gve_tx_dqo.c
> index 1a8eb96ea9..30a1455b20 100644
> --- a/drivers/net/gve/gve_tx_dqo.c
> +++ b/drivers/net/gve/gve_tx_dqo.c
> @@ -116,7 +116,7 @@ gve_tx_burst_dqo(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
>  		first_sw_id = sw_id;
>  		do {
>  			if (sw_ring[sw_id] != NULL)
> -				PMD_DRV_LOG(ERR, "Overwriting an entry in sw_ring");
> +				PMD_DRV_LOG(DEBUG, "Overwriting an entry in sw_ring");
>  
>  			txd = &txr[tx_id];
>  			sw_ring[sw_id] = tx_pkt;

Hi Rushil,

I will continue with this patch, BUT
logging in the datapath has potential problems like this, also it may
have performance impact even log is not printed, because of additional
check in the log function.

For datapath, you can prefer:
- Add log macros controlled by RTE_ETHDEV_DEBUG_RX & RTE_ETHDEV_DEBUG_TX
flags
- Or use RTE_LOG_DP() macro which is compiled out if default log level
is less than the log uses


Also another perspective for the logs, when end-user observes this bloat
of logs, what she can do?
Can she change some driver arguments or environment variables to fix the
issue, if not what is the point of the log?
If this is a condition that can occur dynamically based on received
traffic and user doesn't have control on it, maybe driver should handle
the error without log?
And if this is a log for driver developer, perhaps it should be assert
or similar that is disabled in the release build?