Re: [dpdk-dev] [PATCH] examples: remove Rx checksum offload

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> 
> -----Original Message-----
> > Date: Mon, 30 Jul 2018 11:00:02 +0000
> > From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
> > To: Thomas Monjalon <thomas@monjalon.net>, Jerin Jacob
> >  <jerin.jacob@caviumnetworks.com>
> > CC: "dev@dpdk.org" <dev@dpdk.org>, "Yigit, Ferruh"
> >  <ferruh.yigit@intel.com>, "shahafs@mellanox.com" <shahafs@mellanox.com>
> > Subject: RE: [dpdk-dev] [PATCH] examples: remove Rx checksum offload
> >
> > External Email
> >
> > > -----Original Message-----
> > > From: Thomas Monjalon [mailto:thomas@monjalon.net]
> > > Sent: Monday, July 30, 2018 10:51 AM
> > > To: Jerin Jacob <jerin.jacob@caviumnetworks.com>; Ananyev, Konstantin <konstantin.ananyev@intel.com>
> > > Cc: dev@dpdk.org; Yigit, Ferruh <ferruh.yigit@intel.com>; shahafs@mellanox.com
> > > Subject: Re: [dpdk-dev] [PATCH] examples: remove Rx checksum offload
> > >
> > > 30/07/2018 11:35, Jerin Jacob:
> > > > From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
> > > > > >
> > > > > > As of now, application does not check PKT_RX_*_CKSUM_* flags per
> > > > > > packet, so it does not matter DEV_RX_OFFLOAD_CHECKSUM enabled or not.
> > > > > >
> > > > > > Removing DEV_RX_OFFLOAD_CHECKSUM offload so that driver can save a few
> > > > > > cycles if possible.
> > > > >
> > > > > Personally, I'd move in other direction: keep RX checksum offload and add
> > > > > checks inside sample apps to handle (drop) packets with invalid checksum.
> > > >
> > > > OK. Till someones add the DROP logic in application, Can we take
> > > > this patch? Because there is no point in enabling DEV_RX_OFFLOAD_CHECKSUM
> > > > without DROP or any meaning full action in application.
> >
> > Probably, but at least it gives users a right estimation how long the proper
> > RX/TX routine would take.
> 
> For estimation, application can add any flag they want in local setup.
> It does not need to be upstream with out feature complete.
> 
> > From other side what the point to disable these flags now, if we know that
> 
> At least nicvf Rx routines are crafted based DEV_RX_OFFLOAD_CHECKSUM
> flags. If driver Rx routine crafted such case it will be useful.
> 
> > we are doing wrong thing and will have to re-enable them again in future?
> 
> But it is not correct now either. Right?

Yes, right now invalid cksum information is simply ignored.
As you pointed - some PMD select RX routine based on checksum offload flags.
Yes, removing these flags might produce better performance numbers.
But from my perspective - it would be an artificial and temporary improvement,
as for l3fwd like apps we'll need to revert it back and add code to drop invalid packets.
Konstantin

> 
> >
> > >
> > > If there is no patch sent to use this offload on August 1st,
> > > then I will apply this patch to remove the offload request.
> > >
> >
> > Isn't it too late to do such things right now?
> > We are in RC3 stage and doesn't look like a critical issue.
> 
> Yes. We can add it when have we proper fix. Currently, it signaling a wrong
> interpretation to application.
> 
> 
> > Konstantin
> >
> >