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From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
To: Olivier MATZ <olivier.matz@6wind.com>
Cc: dev@dpdk.org, maxime.coquelin@redhat.com, huawei.xie@intel.com,
	stephen@networkplumber.org, "Tan,
	Jianfeng" <jianfeng.tan@intel.com>,
	Tomasz Kulasek <tomaszx.kulasek@intel.com>,
	Thomas Monjalon <thomas.monjalon@6wind.com>,
	Konstantin Ananyev <konstantin.ananyev@intel.com>
Subject: Re: [dpdk-dev] [PATCH 5/5] net/virtio: fix Tso when mbuf is shared
Date: Sat, 28 Jan 2017 20:32:21 +0800	[thread overview]
Message-ID: <20170128123221.GJ10293@yliu-dev.sh.intel.com> (raw)
In-Reply-To: <20170124115120.2c2667f4@glumotte.dev.6wind.com>

On Tue, Jan 24, 2017 at 11:51:20AM +0100, Olivier MATZ wrote:
> On Wed, 18 Jan 2017 13:03:48 +0800, Yuanhan Liu
> <yuanhan.liu@linux.intel.com> wrote:
> > On Tue, Jan 17, 2017 at 12:18:25PM +0100, Olivier Matz wrote:
> > > > I hope I could have time to dig this further, since, honestly, I
> > > > don't quite like this patch: it makes things un-maintainable.  
> > > 
> > > Well, I'm not that proud of the patch, but that's the best solution
> > > I've found. Nevertheless saying it makes things un-maintainable
> > > looks a bit excessive to me :)  
> > 
> > Aha... really sorry about that!
> > 
> > But honestly, I'd say again, it makes thing more complex, just for
> > fixing a corner and rare issue. I'd try to avoid that.
> > 
> > > 
> > > The option of reallocating a mbuf, copy and fix network headers in
> > > it looks even more complex to me (that was my first approach).
> > >   
> > > > Besides that, I think we have similar issue with nic drivers. See
> > > > the rte_net_intel_cksum_flags_prepare() function introduced at
> > > > commit 4fb7e803eb1a ("ethdev: add Tx preparation").  
> > > 
> > > Yes, that was discussed a bit. See [1] and the subsequent mails.
> > > http://dpdk.org/ml/archives/dev/2016-December/051014.html  
> > 
> > Thanks for the info, and I'm pretty Okay with that.
> > 
> > > My opinion is that tx_burst() should not change the mbuf data, it's
> > > always been like this. For Intel NICs, there is no issue since the
> > > DPDK API is derived from Intel NICs API, so there is no fix to do
> > > in the mbuf data.
> > > 
> > > For tx_prepare(), it's explicitly said that it can update the data.
> > > If tx_prepare() becomes mandatory, it will naturally fix this issue
> > > without modifying the driver, because the phdr csum calculation
> > > will be done in tx_prepare().
> > > 
> > > An alternative is to mark this as a known issue for now, and wait
> > > until tx_prepare() is mandatory.  
> > 
> > I see no reason to wait. Though my understanding is it may not be a
> > mandatory so far, but user is supposed to calculate the pseudo-header
> > checksum by themself before. Now they have one more option:
> > tx_prepare.
> >
> > That means, in either way, user has to do some extra works to make
> > TSO work (either by themself or call tx_prepare). So I don't think
> > it'd be an issue?
> 
> Yes sounds good. I'll check how a tx_prepare() could be implemented for
> virtio, in order to fix this issue.

Thanks.

> In the meanwhile, for the 17.02, I think it could be good to highlight
> the problem in the known issues, what do you think?

Yes, I think it's a good idea.

	--yliu

  reply	other threads:[~2017-01-28 12:29 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-11-24  8:56 [dpdk-dev] [PATCH 0/5] virtio/mbuf: fix virtio tso with shared mbufs Olivier Matz
2016-11-24  8:56 ` [dpdk-dev] [PATCH 1/5] mbuf: remove const attribute in mbuf read function Olivier Matz
2016-11-24  8:56 ` [dpdk-dev] [PATCH 2/5] mbuf: new helper to check if a mbuf is shared Olivier Matz
2016-11-24  8:56 ` [dpdk-dev] [PATCH 3/5] mbuf: new helper to write data in a mbuf chain Olivier Matz
2016-11-24  8:56 ` [dpdk-dev] [PATCH 4/5] mbuf: new helper to copy data from a mbuf Olivier Matz
2016-11-24  8:56 ` [dpdk-dev] [PATCH 5/5] net/virtio: fix Tso when mbuf is shared Olivier Matz
2016-12-14  7:27   ` Yuanhan Liu
2017-01-09 17:46     ` Olivier Matz
2017-01-16  6:48       ` Yuanhan Liu
2017-01-17 11:18         ` Olivier Matz
2017-01-18  5:03           ` Yuanhan Liu
2017-01-24 10:51             ` Olivier MATZ
2017-01-28 12:32               ` Yuanhan Liu [this message]
2017-01-09 17:59   ` Stephen Hemminger

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