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From: Gavin Hu <Gavin.Hu@arm.com>
To: Jerin Jacob <jerinjacobk@gmail.com>
Cc: dpdk-dev <dev@dpdk.org>, nd <nd@arm.com>,
	David Marchand <david.marchand@redhat.com>,
	"thomas@monjalon.net" <thomas@monjalon.net>,
	"rasland@mellanox.com" <rasland@mellanox.com>,
	"maxime.coquelin@redhat.com" <maxime.coquelin@redhat.com>,
	"tiwei.bie@intel.com" <tiwei.bie@intel.com>,
	"hemant.agrawal@nxp.com" <hemant.agrawal@nxp.com>,
	"jerinj@marvell.com" <jerinj@marvell.com>,
	Pavan Nikhilesh <pbhagavatula@marvell.com>,
	Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
	Ruifeng Wang <Ruifeng.Wang@arm.com>,
	Phil Yang <Phil.Yang@arm.com>, Joyce Kong <Joyce.Kong@arm.com>,
	Steve Capper <Steve.Capper@arm.com>, nd <nd@arm.com>
Subject: Re: [dpdk-dev] [PATCH v2 1/3] eal/arm64: relax the io barrier for aarch64
Date: Mon, 23 Dec 2019 10:16:47 +0000
Message-ID: <VI1PR08MB53766C30B5CDA00FB9FCE9678F2E0@VI1PR08MB5376.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <CALBAE1Mqam3Rsqpy6Hhx1NNYCBs1Ed918hbAH_oo35dEvJo1mg@mail.gmail.com>

Hi Jerin,

> -----Original Message-----
> From: Jerin Jacob <jerinjacobk@gmail.com>
> Sent: Monday, December 23, 2019 5:20 PM
> To: Gavin Hu <Gavin.Hu@arm.com>
> Cc: dpdk-dev <dev@dpdk.org>; nd <nd@arm.com>; David Marchand
> <david.marchand@redhat.com>; thomas@monjalon.net;
> rasland@mellanox.com; maxime.coquelin@redhat.com;
> tiwei.bie@intel.com; hemant.agrawal@nxp.com; jerinj@marvell.com;
> Pavan Nikhilesh <pbhagavatula@marvell.com>; Honnappa Nagarahalli
> <Honnappa.Nagarahalli@arm.com>; Ruifeng Wang
> <Ruifeng.Wang@arm.com>; Phil Yang <Phil.Yang@arm.com>; Joyce Kong
> <Joyce.Kong@arm.com>; Steve Capper <Steve.Capper@arm.com>
> Subject: Re: [dpdk-dev] [PATCH v2 1/3] eal/arm64: relax the io barrier for
> aarch64
> 
> On Mon, Dec 23, 2019 at 2:44 PM Gavin Hu <Gavin.Hu@arm.com> wrote:
> >
> > Hi Jerin,
> 
> Hi Gavin,
> 
> >
> > I think we are on the same page with regard to the problem, and the
> situations, thanks for illuminating the historical background of the two
> barriers.
> > About the solution, I added inline comments.
> > > It will be optimization only when if we are changing in the fast path.
> > > In the slow path, it does not matter.
> > > I think, the First step should be to use rte_cio_* wherever it is
> > > coherent memory used in _fast path_. I think, Almost every driver
> > > fixed that.
> > >
> > > I am not against this patch(changing the slow path to use rte_cio*
> > > from rte_io* and virtio changes associated with that).
> > > If you are taking that patch, pay attention to all the drivers in the
> > > tree which is using rte_io* for mixed access in slowpath.
> > I see 30+ drivers has calling rte_io* directly or indirectly through
> rte_write/read*.
> > It is hard for me to figure out all the mixed accesses in these drivers, and
> as you said, it makes no sense to change the _slow path_.
> >
> > How about we keep the old rte_io as is, and introduce 'fast path' version
> of rte_io for new code use?
> > Then in future, we may merge the two?
> > Another reason about this proposal is maybe there is rte_io calling in the
> fast path, but they are not mixed accesses and rte_cio is not suitable.
> 
> Could you share more details about the case where fastpath + rte_io
> needed + rte_cio is not suitable?

Here is an example for i40e, in the fast path, but only a pure io memory access. 
https://code.dpdk.org/dpdk/v19.11/source/drivers/net/i40e/i40e_rxtx.c#L1208

I wanted two variants of rte_io, because also x86 requires two as indicated here, one for no-WC and another for WC.
http://inbox.dpdk.org/dev/20191204151916.12607-1-xiaoyun.li@intel.com/T/#ea8bb1b4a378ab09baedbf95b4542bcb92f4a396f 
> 
> >
> > Any thoughts?
> >
> > >
> > > > But as the case in i40e, we must pay attention to where rte_cio was
> > > missing but rescued by old rte_io(but not by new rte_io).
> > > >
> > > >

  reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-22 15:27 [dpdk-dev] [PATCH v1 0/3] relax io barrier for aarch64 and use smp barriers for virtual pci memory Gavin Hu
2019-10-22 15:27 ` [dpdk-dev] [PATCH v1 1/3] eal/arm64: relax the io barrier for aarch64 Gavin Hu
2019-10-22 15:27 ` [dpdk-dev] [PATCH v1 2/3] net/virtio: virtual PCI requires smp barriers Gavin Hu
2019-10-22 15:27 ` [dpdk-dev] [PATCH v1 3/3] crypto/virtio: " Gavin Hu
2019-10-23  8:22 ` [dpdk-dev] [PATCH v1 0/3] relax io barrier for aarch64 and use smp barriers for virtual pci memory Maxime Coquelin
2019-11-07  1:13   ` Gavin Hu (Arm Technology China)
2019-12-20  3:09 ` [dpdk-dev] [PATCH v2 " Gavin Hu
2019-12-20  3:09 ` [dpdk-dev] [PATCH v2 1/3] eal/arm64: relax the io barrier for aarch64 Gavin Hu
2019-12-20  3:33   ` Jerin Jacob
2019-12-20  3:38     ` Jerin Jacob
2019-12-20  4:19       ` Gavin Hu
2019-12-20  4:34         ` Jerin Jacob
2019-12-20  6:32           ` Gavin Hu
2019-12-20  6:55             ` Jerin Jacob
2019-12-23  9:14               ` Gavin Hu
2019-12-23  9:19                 ` Jerin Jacob
2019-12-23 10:16                   ` Gavin Hu [this message]
2020-01-02  9:51                     ` Jerin Jacob
2020-01-03  6:30                       ` Gavin Hu
2020-01-03  7:34                         ` Jerin Jacob
2020-01-03  9:12                           ` Gavin Hu
2019-12-20  3:09 ` [dpdk-dev] [PATCH v2 2/3] net/virtio: virtual PCI requires smp barriers Gavin Hu
2019-12-20  8:17   ` Tiwei Bie
2019-12-20 10:19     ` Gavin Hu
2019-12-20  3:09 ` [dpdk-dev] [PATCH v2 3/3] crypto/virtio: " Gavin Hu
2020-02-08 13:48 ` [dpdk-dev] [PATCH v3] net/i40e: relaxed barrier in the tx fastpath Gavin Hu
2020-02-11  2:11   ` Ye Xiaolong
2020-02-12  6:02     ` Gavin Hu
2020-02-15  8:25   ` Jerin Jacob
2020-02-12  5:56 ` [dpdk-dev] [PATCH v4] " Gavin Hu
2020-02-15 15:16   ` Ye Xiaolong
2020-02-16  9:51     ` Thomas Monjalon
2020-02-16 16:38       ` Ye Xiaolong
2020-02-16 17:36         ` Thomas Monjalon

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