Re: [dpdk-dev] [PATCH] app/testpmd: do not enable Rx offloads by default

["Lu, Wenzhuo" <wenzhuo.lu@intel.com>]

Hi Thomas,

> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas@monjalon.net]
> Sent: Thursday, January 25, 2018 5:04 PM
> To: Lu, Wenzhuo <wenzhuo.lu@intel.com>
> Cc: Moti Haimovsky <motih@mellanox.com>; dev@dpdk.org;
> shahafs@mellanox.com; Yigit, Ferruh <ferruh.yigit@intel.com>
> Subject: Re: [PATCH] app/testpmd: do not enable Rx offloads by default
> 
> 25/01/2018 02:11, Lu, Wenzhuo:
> > > --- a/app/test-pmd/testpmd.c
> > > +++ b/app/test-pmd/testpmd.c
> > > @@ -305,9 +305,7 @@ struct fwd_engine * fwd_engines[] = {
> > >   */
> > >  struct rte_eth_rxmode rx_mode = {
> > >  	.max_rx_pkt_len = ETHER_MAX_LEN, /**< Default maximum frame
> > > length. */
> > > -	.offloads = (DEV_RX_OFFLOAD_VLAN_FILTER |
> > > -		     DEV_RX_OFFLOAD_VLAN_STRIP |
> > > -		     DEV_RX_OFFLOAD_CRC_STRIP),
> > > +	.offloads = 0,
> >
> > Change the default behavior may trigger other problems. I think TX offload
> could be a good reference. Get the capability and check what's supported
> first, then ignore the not supported functions with printing a warning but
> not block anything...
> 
> I agree that we should check the capabilities before requesting an offload.
> But I disagree on another point: we should not enable an offload if the user
> did not request it explicitly. It makes things unclear.
> This is a testing tool, it should be close to the ethdev API behavior.
> 
> Why these offload flags are silently enabled?
I don't think it's silently. It's a global configuration. In this case, testpmd is the user, it does request it explicitly. If it's not so explicit, maybe we can consider moving all the configuration to a specific configure file.
Talking about why it's enabled by default. Hard to figure out the history. To my opinion, the original designer wants to simulate the common case.