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From: Flavio Leitner <fbl@sysclose.org>
To: Olivier Matz <olivier.matz@6wind.com>
Cc: David Marchand <david.marchand@redhat.com>,
	dev@dpdk.org, maxime.coquelin@redhat.com, i.maximets@ovn.org,
	Keith Wiles <keith.wiles@intel.com>
Subject: Re: [dpdk-dev] [PATCH 2/5] net/tap: do not touch Tx offload flags
Date: Thu, 8 Apr 2021 09:58:35 -0300
Message-ID: <YG79++CcXIW6PTDh@p50.lan> (raw)
In-Reply-To: <20210408120521.GW1650@platinum>

On Thu, Apr 08, 2021 at 02:05:21PM +0200, Olivier Matz wrote:
> On Thu, Apr 08, 2021 at 08:21:58AM -0300, Flavio Leitner wrote:
> > On Thu, Apr 08, 2021 at 09:41:59AM +0200, Olivier Matz wrote:
> > > On Wed, Apr 07, 2021 at 05:15:39PM -0300, Flavio Leitner wrote:
> > > > On Thu, Apr 01, 2021 at 11:52:40AM +0200, David Marchand wrote:
> > > > > Tx offload flags are of the application responsibility.
> > > > > Leave the mbuf alone and check for TSO where needed.
> > > > > 
> > > > > Signed-off-by: David Marchand <david.marchand@redhat.com>
> > > > > ---
> > > > 
> > > > The patch looks good, but maybe a better approach would be
> > > > to change the documentation to require the TCP_CKSUM flag
> > > > when TCP_SEG is used, otherwise this flag adjusting needs
> > > > to be replicated every time TCP_SEG is used.
> > > > 
> > > > The above could break existing applications, so perhaps doing
> > > > something like below would be better and backwards compatible?
> > > > Then we can remove those places tweaking the flags completely.
> > > 
> > > As a first step, I suggest to document that:
> > > - applications must set TCP_CKSUM when setting TCP_SEG
> > 
> > That's what I suggest above.
> > 
> > > - pmds must suppose that TCP_CKSUM is set when TCP_SEG is set
> > 
> > But that keeps the problem of implying the TCP_CKSUM flag in
> > various places.
> 
> Yes. What I propose is just a first step: better document what is the
> current expected behavior, before doing something else.
> 
> > > This is clearer that what we have today, and I think it does not break
> > > anything. This will guide apps in the correct direction, facilitating
> > > an eventual future PMD change.
> > > 
> > > > diff --git a/lib/librte_mbuf/rte_mbuf_core.h b/lib/librte_mbuf/rte_mbuf_core.h
> > > > index c17dc95c5..6a0c2cdd9 100644
> > > > --- a/lib/librte_mbuf/rte_mbuf_core.h
> > > > +++ b/lib/librte_mbuf/rte_mbuf_core.h
> > > > @@ -298,7 +298,7 @@ extern "C" {
> > > >   *  - if it's IPv4, set the PKT_TX_IP_CKSUM flag
> > > >   *  - fill the mbuf offload information: l2_len, l3_len, l4_len, tso_segsz
> > > >   */
> > > > -#define PKT_TX_TCP_SEG       (1ULL << 50)
> > > > +#define PKT_TX_TCP_SEG       (1ULL << 50) | PKT_TX_TCP_CKSUM
> > > >  
> > > >  /** TX IEEE1588 packet to timestamp. */
> > > >  #define PKT_TX_IEEE1588_TMST (1ULL << 51)
> > > 
> > > I'm afraid some applications or drivers use extended bit manipulations
> > > to do the conversion from/to another domain (like hardware descriptors
> > > or application-specific flags). They may expect this constant to be a
> > > uniq flag.
> > 
> > Interesting, do you have an example? Because each flag still has an
> > separate meaning.
> 
> Honnestly no, I don't have any good example, just a (maybe unfounded) doubt.
> 
> I have in mind operations that are done with tables or vector
> instructions inside the drivers, but this is mainly done for Rx, not Tx.
> You can look at Tx functions like mlx5_set_cksum_table() or
> nix_xmit_pkts_vector(), or Rx functions like desc_to_olflags_v() or
> enic_noscatter_vec_recv_pkts() to see what kind of stuff I'm talking
> about.

I see your point. Going back to improving the documentation as a
first step, what would be the next steps? Are we going to wait few
releases and then remove the flag tweaking code assuming that PMDs
and apps are ok?

Thanks,
-- 
fbl

  reply	other threads:[~2021-04-08 12:58 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-01  9:52 [dpdk-dev] [PATCH 0/5] Offload flags fixes David Marchand
2021-04-01  9:52 ` [dpdk-dev] [PATCH 1/5] mbuf: mark old offload flag as deprecated David Marchand
2021-04-07 20:14   ` Flavio Leitner
2021-04-08  7:23   ` Olivier Matz
2021-04-08  8:41     ` David Marchand
2021-04-01  9:52 ` [dpdk-dev] [PATCH 2/5] net/tap: do not touch Tx offload flags David Marchand
2021-04-07 20:15   ` Flavio Leitner
2021-04-08  7:41     ` Olivier Matz
2021-04-08 11:21       ` Flavio Leitner
2021-04-08 12:05         ` Olivier Matz
2021-04-08 12:58           ` Flavio Leitner [this message]
2021-04-09 13:30             ` Olivier Matz
2021-04-09 16:55               ` Flavio Leitner
2021-04-28 12:17               ` David Marchand
2021-04-08 12:16         ` Ananyev, Konstantin
2021-04-08  7:53   ` Olivier Matz
2021-04-28 12:12     ` David Marchand
2021-04-01  9:52 ` [dpdk-dev] [PATCH 3/5] net/virtio: " David Marchand
2021-04-13 14:17   ` Maxime Coquelin
2021-04-01  9:52 ` [dpdk-dev] [PATCH 4/5] net/virtio: refactor Tx offload helper David Marchand
2021-04-08 13:05   ` Flavio Leitner
2021-04-09  2:31   ` Ruifeng Wang
2021-04-01  9:52 ` [dpdk-dev] [PATCH 5/5] vhost: fix offload flags in Rx path David Marchand
2021-04-08  8:28   ` Olivier Matz
2021-04-08 18:38   ` Flavio Leitner
2021-04-13 15:27     ` Maxime Coquelin
2021-04-27 17:09       ` David Marchand
2021-04-27 17:19         ` David Marchand
2021-04-29  8:04 ` [dpdk-dev] [PATCH v2 0/4] Offload flags fixes David Marchand
2021-04-29  8:04   ` [dpdk-dev] [PATCH v2 1/4] mbuf: mark old offload flag as deprecated David Marchand
2021-04-29 12:14     ` Lance Richardson
2021-04-29 16:45     ` Ajit Khaparde
2021-04-29  8:04   ` [dpdk-dev] [PATCH v2 2/4] net/virtio: do not touch Tx offload flags David Marchand
2021-04-29 13:51     ` Flavio Leitner
2021-04-29  8:04   ` [dpdk-dev] [PATCH v2 3/4] net/virtio: refactor Tx offload helper David Marchand
2021-04-29 12:59     ` Maxime Coquelin
2021-04-29  8:04   ` [dpdk-dev] [PATCH v2 4/4] vhost: fix offload flags in Rx path David Marchand
2021-04-29 13:30     ` Maxime Coquelin
2021-04-29 13:31       ` Maxime Coquelin
2021-04-29 20:21         ` David Marchand
2021-04-30  8:38           ` Maxime Coquelin
2021-04-29 20:09       ` David Marchand
2021-04-29 18:39     ` Flavio Leitner
2021-04-29 19:18       ` David Marchand
2021-05-03 13:26 ` [dpdk-dev] [PATCH v3 0/4] Offload flags fixes David Marchand
2021-05-03 13:26   ` [dpdk-dev] [PATCH v3 1/4] mbuf: mark old offload flag as deprecated David Marchand
2021-05-03 14:02     ` Maxime Coquelin
2021-05-03 14:12     ` David Marchand
2021-05-03 13:26   ` [dpdk-dev] [PATCH v3 2/4] net/virtio: do not touch Tx offload flags David Marchand
2021-05-03 13:26   ` [dpdk-dev] [PATCH v3 3/4] net/virtio: refactor Tx offload helper David Marchand
2021-05-03 13:26   ` [dpdk-dev] [PATCH v3 4/4] vhost: fix offload flags in Rx path David Marchand
2021-05-03 15:24   ` [dpdk-dev] [PATCH v3 0/4] Offload flags fixes Maxime Coquelin
2021-05-03 16:21     ` David Marchand
2021-05-03 16:43 ` [dpdk-dev] [PATCH v4 0/3] " David Marchand
2021-05-03 16:43   ` [dpdk-dev] [PATCH v4 1/3] net/virtio: do not touch Tx offload flags David Marchand
2021-05-03 16:43   ` [dpdk-dev] [PATCH v4 2/3] net/virtio: refactor Tx offload helper David Marchand
2021-05-03 16:43   ` [dpdk-dev] [PATCH v4 3/3] vhost: fix offload flags in Rx path David Marchand
2021-05-04 11:07     ` Flavio Leitner
2021-05-08  6:24     ` Wang, Yinan
2021-05-12  3:29       ` Wang, Yinan
2021-05-12 15:20         ` David Marchand
2021-05-13  6:34           ` Wang, Yinan
2021-05-04  8:29   ` [dpdk-dev] [PATCH v4 0/3] Offload flags fixes Maxime Coquelin

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