Re: [PATCH net-next v5 04/10] net: psample: allow using rate as probability

[Ido Schimmel]

On Tue, Jun 25, 2024 at 10:51:47PM +0200, Adrian Moreno wrote:
> Although not explicitly documented in the psample module itself, the
> definition of PSAMPLE_ATTR_SAMPLE_RATE seems inherited from act_sample.
> 
> Quoting tc-sample(8):
> "RATE of 100 will lead to an average of one sampled packet out of every
> 100 observed."
> 
> With this semantics, the rates that we can express with an unsigned
> 32-bits number are very unevenly distributed and concentrated towards
> "sampling few packets".
> For example, we can express a probability of 2.32E-8% but we
> cannot express anything between 100% and 50%.
> 
> For sampling applications that are capable of sampling a decent
> amount of packets, this sampling rate semantics is not very useful.
> 
> Add a new flag to the uAPI that indicates that the sampling rate is
> expressed in scaled probability, this is:
> - 0 is 0% probability, no packets get sampled.
> - U32_MAX is 100% probability, all packets get sampled.
> 
> Signed-off-by: Adrian Moreno <amorenoz@xxxxxxxxxx>

Reviewed-by: Ido Schimmel <idosch@xxxxxxxxxx>