Re: [PATCH] net/i40e: increase descriptor queue length to 8160

[Bruce Richardson <bruce.richardson@intel.com>]

On Tue, Jun 18, 2024 at 01:12:13PM +0100, Bruce Richardson wrote:
> On Mon, May 27, 2024 at 07:19:21PM +0300, Igor Gutorov wrote:
> > According to the Intel X710/XXV710/XL710 Datasheet, the maximum receive
> > queue descriptor length is 0x1FE0 (8160 in base 10). This is specified
> > as QLEN in table 8-12, page 1083.
> > 
> > I've tested this change with an XXV710 NIC and it has positive effect on
> > performance under high load scenarios. Where previously I'd get
> > ~2000 packets/sec miss rate, now I get only ~40 packets/sec miss rate.
> > 
> > Signed-off-by: Igor Gutorov <igootorov@gmail.com>
> > ---
> >  drivers/net/i40e/i40e_rxtx.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/i40e/i40e_rxtx.h b/drivers/net/i40e/i40e_rxtx.h
> > index 2f2f890855..33fc9770d9 100644
> > --- a/drivers/net/i40e/i40e_rxtx.h
> > +++ b/drivers/net/i40e/i40e_rxtx.h
> > @@ -25,7 +25,7 @@
> >  #define I40E_RX_MAX_DATA_BUF_SIZE	(16 * 1024 - 128)
> >  
> >  #define	I40E_MIN_RING_DESC	64
> > -#define	I40E_MAX_RING_DESC	4096
> > +#define	I40E_MAX_RING_DESC	8160
> >  
> 
> since the ring memory allocation in the driver always seems to allocate
> space for up to the max number of descriptors, this will lead to an
> increase of memory footprint of ~128k per Rx Q, and ~64k per Tx Q. However,
> I'd view this as relatively harmless given what we have now. If it is an
> issue, we should look to fix it in a separate patch, rather than blocking
> this simple change.
> 
> Acked-by: Bruce Richardson <bruce.richardson@intel.com>

Patch applied to dpdk-next-net-intel,

Thanks,
/Bruce