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From: Bruce Richardson <bruce.richardson@intel.com>
To: Morten Brørup <mb@smartsharesystems.com>
Cc: Thomas Monjalon <thomas@monjalon.net>,
	dev@dpdk.org, techboard@dpdk.org,
	Ajit Khaparde <ajit.khaparde@broadcom.com>,
	"Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
	Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>,
	"Yigit, Ferruh" <ferruh.yigit@intel.com>,
	david.marchand@redhat.com, olivier.matz@6wind.com,
	jerinj@marvell.com, viacheslavo@nvidia.com,
	honnappa.nagarahalli@arm.com, maxime.coquelin@redhat.com,
	stephen@networkplumber.org, hemant.agrawal@nxp.com,
	Matan Azrad <matan@nvidia.com>,
	Shahaf Shuler <shahafs@nvidia.com>
Subject: Re: [dpdk-dev] [PATCH 15/15] mbuf: move pool pointer in hotterfirst half
Date: Tue, 3 Nov 2020 13:50:25 +0000
Message-ID: <20201103135025.GD1144@bricha3-MOBL.ger.corp.intel.com> (raw)
In-Reply-To: <98CBD80474FA8B44BF855DF32C47DC35C613DC@smartserver.smartshare.dk>

On Tue, Nov 03, 2020 at 02:46:17PM +0100, Morten Brørup wrote:
> > From: Bruce Richardson [mailto:bruce.richardson@intel.com]
> > Sent: Tuesday, November 3, 2020 1:26 PM
> > 
> > On Tue, Nov 03, 2020 at 01:10:05PM +0100, Morten Brørup wrote:
> > > > From: Thomas Monjalon [mailto:thomas@monjalon.net]
> > > > Sent: Monday, November 2, 2020 4:58 PM
> > > >
> > > > +Cc techboard
> > > >
> > > > We need benchmark numbers in order to take a decision.
> > > > Please all, prepare some arguments and numbers so we can discuss
> > > > the mbuf layout in the next techboard meeting.
> > >
> > > I propose that the techboard considers this from two angels:
> > >
> > > 1. Long term goals and their relative priority. I.e. what can be
> > > achieved with wide-ranging modifications, requiring yet another ABI
> > > break and due notices.
> > >
> > > 2. Short term goals, i.e. what can be achieved for this release.
> > >
> > >
> > > My suggestions follow...
> > >
> > > 1. Regarding long term goals:
> > >
> > > I have argued that simple forwarding of non-segmented packets using
> > > only the first mbuf cache line can be achieved by making three
> > > modifications:
> > >
> > > a) Move m->tx_offload to the first cache line.
> > > b) Use an 8 bit pktmbuf mempool index in the first cache line,
> > >    instead of the 64 bit m->pool pointer in the second cache line.
> > > c) Do not access m->next when we know that it is NULL.
> > >    We can use m->nb_segs == 1 or some other invariant as the gate.
> > >    It can be implemented by adding an m->next accessor function:
> > >    struct rte_mbuf * rte_mbuf_next(struct rte_mbuf * m)
> > >    {
> > >        return m->nb_segs == 1 ? NULL : m->next;
> > >    }
> > >
> > > Regarding the priority of this goal, I guess that simple forwarding
> > > of non-segmented packets is probably the path taken by the majority
> > > of packets handled by DPDK.
> > >
> > >
> > > An alternative goal could be:
> > > Do not touch the second cache line during RX.
> > > A comment in the mbuf structure says so, but it is not true anymore.
> > >
> > 
> > The comment should be true for non-scattered RX, I believe.
> 
> You are correct.
> 
> My suggestion was unclear: Extend this remark to include segmented packets.
> 
> This could be a priority if the techboard considers RX segmented packets more important than my suggestion for single cache line forwarding of non-segmented packets.
> 
> 
> > I'm not aware of any use of second cacheline for the fast-path RXs for many drivers.
> > Am I missing something that has changed recently here?
> 
> Check out eth_igb_recv_pkts() in the E1000 driver: rxm->next = NULL;
> Or pmd_rx_burst() in the TAP driver: new_tail->next = seg->next;
> 
> Perhaps the documentation should describe best practices for implementing RX and TX functions in drivers, including allocating/freeing mbufs. Or an example dummy Ethernet driver could do it.
> 

Yes, perhaps I should be clearer about the "fast-path", because I was
thinking of the optimized RX/TX paths for those nics at 10G and above.
Probably the documentation should indeed have an update clarifying things a
bit, since using the first cacheline only possible but not mandatory for
simple RX.

/Bruce

  reply	other threads:[~2020-11-03 13:50 UTC|newest]

Thread overview: 170+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-29  9:27 [dpdk-dev] [PATCH 00/15] remove mbuf timestamp Thomas Monjalon
2020-10-29  9:27 ` [dpdk-dev] [PATCH 01/15] eventdev: remove software Rx timestamp Thomas Monjalon
2020-10-29  9:27 ` [dpdk-dev] [PATCH 02/15] mbuf: add Rx timestamp dynamic flag Thomas Monjalon
2020-10-29  9:58   ` Andrew Rybchenko
2020-10-29 18:19     ` Ajit Khaparde
2020-10-29  9:27 ` [dpdk-dev] [PATCH 03/15] ethdev: register mbuf field and flags for timestamp Thomas Monjalon
2020-10-29 10:08   ` Andrew Rybchenko
2020-10-29 10:12     ` Thomas Monjalon
2020-10-29 10:33       ` Andrew Rybchenko
2020-10-29 10:46         ` Thomas Monjalon
2020-10-29  9:27 ` [dpdk-dev] [PATCH 04/15] latency: switch timestamp to dynamic mbuf field Thomas Monjalon
2020-10-29 10:13   ` Andrew Rybchenko
2020-10-29 10:40     ` Thomas Monjalon
2020-10-29 14:20   ` Pattan, Reshma
2020-10-29 16:15     ` Thomas Monjalon
2020-10-29  9:27 ` [dpdk-dev] [PATCH 05/15] net/ark: " Thomas Monjalon
2020-10-29  9:27 ` [dpdk-dev] [PATCH 06/15] net/dpaa2: " Thomas Monjalon
2020-10-29  9:27 ` [dpdk-dev] [PATCH 07/15] net/mlx5: fix dynamic mbuf offset lookup check Thomas Monjalon
2020-10-29  9:27 ` [dpdk-dev] [PATCH 08/15] net/mlx5: switch timestamp to dynamic mbuf field Thomas Monjalon
2020-10-29  9:27 ` [dpdk-dev] [PATCH 09/15] net/nfb: " Thomas Monjalon
2020-10-29  9:27 ` [dpdk-dev] [PATCH 10/15] net/octeontx2: " Thomas Monjalon
2020-10-29 11:02   ` Andrew Rybchenko
2020-10-29 11:34     ` Thomas Monjalon
2020-10-29 11:37       ` Andrew Rybchenko
2020-10-29 11:52     ` Slava Ovsiienko
2020-10-30 12:41       ` Jerin Jacob
2020-11-01 16:12         ` Thomas Monjalon
2020-11-01 20:00         ` Andrew Rybchenko
2020-10-29  9:27 ` [dpdk-dev] [PATCH 11/15] net/pcap: " Thomas Monjalon
2020-10-29  9:27 ` [dpdk-dev] [PATCH 12/15] app/testpmd: " Thomas Monjalon
2020-10-29 10:20   ` Andrew Rybchenko
2020-10-29 10:43     ` Thomas Monjalon
2020-10-29 10:52       ` Andrew Rybchenko
2020-10-29  9:27 ` [dpdk-dev] [PATCH 13/15] examples/rxtx_callbacks: switch timestamp to dynamic field Thomas Monjalon
2020-10-29 10:21   ` Andrew Rybchenko
2020-10-29 10:44     ` Thomas Monjalon
2020-10-29  9:27 ` [dpdk-dev] [PATCH 14/15] mbuf: remove deprecated timestamp field Thomas Monjalon
2020-10-29 10:23   ` Andrew Rybchenko
2020-10-29 18:18     ` Ajit Khaparde
2020-10-29 14:48   ` Kinsella, Ray
2020-10-29  9:27 ` [dpdk-dev] [PATCH 15/15] mbuf: move pool pointer in hotter first half Thomas Monjalon
2020-10-29 10:50   ` Andrew Rybchenko
2020-10-29 10:56     ` Thomas Monjalon
2020-10-29 14:15       ` Ananyev, Konstantin
2020-10-29 18:45         ` Ajit Khaparde
2020-10-31 18:20           ` [dpdk-dev] [PATCH 15/15] mbuf: move pool pointer in hotterfirst half Morten Brørup
2020-10-31 20:40             ` Thomas Monjalon
2020-11-01  9:12               ` Morten Brørup
2020-11-01 16:21                 ` Thomas Monjalon
2020-11-01 16:38                 ` Thomas Monjalon
2020-11-01 20:59                   ` Morten Brørup
2020-11-02 15:58                     ` Thomas Monjalon
2020-11-03 12:10                       ` Morten Brørup
2020-11-03 12:25                         ` Bruce Richardson
2020-11-03 13:46                           ` Morten Brørup
2020-11-03 13:50                             ` Bruce Richardson [this message]
2020-11-03 14:03                               ` Morten Brørup
2020-11-03 14:02                         ` Slava Ovsiienko
2020-11-03 15:03                           ` Morten Brørup
2020-11-04 15:00                             ` Olivier Matz
2020-11-05  0:25                               ` Ananyev, Konstantin
2020-11-05  9:04                                 ` Morten Brørup
2020-11-05  9:35                                 ` Morten Brørup
2020-11-05 10:29                                   ` Bruce Richardson
2020-10-29 14:42   ` [dpdk-dev] [PATCH 15/15] mbuf: move pool pointer in hotter first half Kinsella, Ray
2020-11-01 18:06 ` [dpdk-dev] [PATCH v2 00/14] remove mbuf timestamp Thomas Monjalon
2020-11-01 18:06   ` [dpdk-dev] [PATCH v2 01/14] eventdev: remove software Rx timestamp Thomas Monjalon
2020-11-01 18:06   ` [dpdk-dev] [PATCH v2 02/14] mbuf: add Rx timestamp dynamic flag Thomas Monjalon
2020-11-01 18:06   ` [dpdk-dev] [PATCH v2 03/14] ethdev: register mbuf field and flags for timestamp Thomas Monjalon
2020-11-02 15:39     ` Olivier Matz
2020-11-02 16:52       ` Thomas Monjalon
2020-11-01 18:06   ` [dpdk-dev] [PATCH v2 04/14] latency: switch timestamp to dynamic mbuf field Thomas Monjalon
2020-11-01 18:06   ` [dpdk-dev] [PATCH v2 05/14] net/ark: " Thomas Monjalon
2020-11-02 15:32     ` Olivier Matz
2020-11-02 16:10       ` Thomas Monjalon
2020-11-01 18:06   ` [dpdk-dev] [PATCH v2 06/14] net/dpaa2: " Thomas Monjalon
2020-11-01 18:06   ` [dpdk-dev] [PATCH v2 07/14] net/mlx5: fix dynamic mbuf offset lookup check Thomas Monjalon
2020-11-01 18:06   ` [dpdk-dev] [PATCH v2 08/14] net/mlx5: switch timestamp to dynamic mbuf field Thomas Monjalon
2020-11-02  5:08     ` Ruifeng Wang
2020-11-02 23:20     ` David Christensen
2020-11-01 18:06   ` [dpdk-dev] [PATCH v2 09/14] net/nfb: " Thomas Monjalon
2020-11-01 18:06   ` [dpdk-dev] [PATCH v2 10/14] net/octeontx2: " Thomas Monjalon
2020-11-01 18:28     ` Jerin Jacob
2020-11-02  9:38       ` Thomas Monjalon
2020-11-02 11:01         ` Thomas Monjalon
2020-11-01 18:06   ` [dpdk-dev] [PATCH v2 11/14] net/pcap: " Thomas Monjalon
2020-11-01 18:06   ` [dpdk-dev] [PATCH v2 12/14] app/testpmd: " Thomas Monjalon
2020-11-01 18:06   ` [dpdk-dev] [PATCH v2 13/14] examples/rxtx_callbacks: switch timestamp to dynamic field Thomas Monjalon
2020-11-01 18:06   ` [dpdk-dev] [PATCH v2 14/14] mbuf: remove deprecated timestamp field Thomas Monjalon
2020-11-02 15:41     ` Olivier Matz
2020-11-02 15:47       ` David Marchand
2020-11-02 15:49         ` Thomas Monjalon
2020-11-01 18:08   ` [dpdk-dev] [PATCH v2 00/14] remove mbuf timestamp Thomas Monjalon
2020-11-03  0:13 ` [dpdk-dev] [PATCH v3 00/16] " Thomas Monjalon
2020-11-03  0:13   ` [dpdk-dev] [PATCH v3 01/16] eventdev: remove software Rx timestamp Thomas Monjalon
2020-11-03  0:13   ` [dpdk-dev] [PATCH v3 02/16] mbuf: add Rx timestamp flag and helpers Thomas Monjalon
2020-11-03  9:33     ` Olivier Matz
2020-11-03  9:59       ` Thomas Monjalon
2020-11-03  0:13   ` [dpdk-dev] [PATCH v3 03/16] latency: switch Rx timestamp to dynamic mbuf field Thomas Monjalon
2020-11-03  0:13   ` [dpdk-dev] [PATCH v3 04/16] net/ark: " Thomas Monjalon
2020-11-03  0:13   ` [dpdk-dev] [PATCH v3 05/16] net/dpaa2: " Thomas Monjalon
2020-11-03  9:18     ` Hemant Agrawal
2020-11-03  0:13   ` [dpdk-dev] [PATCH v3 06/16] net/mlx5: fix dynamic mbuf offset lookup check Thomas Monjalon
2020-11-03  8:12     ` Slava Ovsiienko
2020-11-03  0:13   ` [dpdk-dev] [PATCH v3 07/16] net/mlx5: switch Rx timestamp to dynamic mbuf field Thomas Monjalon
2020-11-03  8:12     ` Slava Ovsiienko
2020-11-03  0:13   ` [dpdk-dev] [PATCH v3 08/16] net/nfb: " Thomas Monjalon
2020-11-03 10:20     ` Olivier Matz
2020-11-03  0:14   ` [dpdk-dev] [PATCH v3 09/16] net/octeontx2: " Thomas Monjalon
2020-11-03 10:52     ` Harman Kalra
2020-11-03 11:22       ` Thomas Monjalon
2020-11-03 12:21         ` Thomas Monjalon
2020-11-03 14:23           ` [dpdk-dev] [EXT] " Harman Kalra
2020-11-03  0:14   ` [dpdk-dev] [PATCH v3 10/16] net/pcap: " Thomas Monjalon
2020-11-03  0:14   ` [dpdk-dev] [PATCH v3 11/16] app/testpmd: " Thomas Monjalon
2020-11-03 10:23     ` Olivier Matz
2020-11-03  0:14   ` [dpdk-dev] [PATCH v3 12/16] examples/rxtx_callbacks: switch timestamp to dynamic field Thomas Monjalon
2020-11-03  0:14   ` [dpdk-dev] [PATCH v3 13/16] ethdev: add doxygen comment for Rx timestamp API Thomas Monjalon
2020-11-03  0:14   ` [dpdk-dev] [PATCH v3 14/16] mbuf: remove deprecated timestamp field Thomas Monjalon
2020-11-03  0:14   ` [dpdk-dev] [PATCH v3 15/16] mbuf: add Tx timestamp registration helper Thomas Monjalon
2020-11-03  0:14   ` [dpdk-dev] [PATCH v3 16/16] ethdev: include mbuf registration in Tx timestamp API Thomas Monjalon
2020-11-03  7:54     ` Slava Ovsiienko
2020-11-03  9:00   ` [dpdk-dev] [PATCH v3 00/16] remove mbuf timestamp David Marchand
2020-11-03 12:21 ` [dpdk-dev] [PATCH v4 " Thomas Monjalon
2020-11-03 12:21   ` [dpdk-dev] [PATCH v4 01/16] eventdev: remove software Rx timestamp Thomas Monjalon
2020-11-03 12:21   ` [dpdk-dev] [PATCH v4 02/16] mbuf: add Rx timestamp flag and helpers Thomas Monjalon
2020-11-03 12:34     ` Andrew Rybchenko
2020-11-03 12:21   ` [dpdk-dev] [PATCH v4 03/16] latency: switch Rx timestamp to dynamic mbuf field Thomas Monjalon
2020-11-03 12:21   ` [dpdk-dev] [PATCH v4 04/16] net/ark: " Thomas Monjalon
2020-11-03 12:37     ` Andrew Rybchenko
2020-11-03 13:08       ` Thomas Monjalon
2020-11-03 12:21   ` [dpdk-dev] [PATCH v4 05/16] net/dpaa2: " Thomas Monjalon
2020-11-03 12:21   ` [dpdk-dev] [PATCH v4 06/16] net/mlx5: fix dynamic mbuf offset lookup check Thomas Monjalon
2020-11-03 12:21   ` [dpdk-dev] [PATCH v4 07/16] net/mlx5: switch Rx timestamp to dynamic mbuf field Thomas Monjalon
2020-11-03 12:21   ` [dpdk-dev] [PATCH v4 08/16] net/nfb: " Thomas Monjalon
2020-11-03 12:21   ` [dpdk-dev] [PATCH v4 09/16] net/octeontx2: " Thomas Monjalon
2020-11-03 12:21   ` [dpdk-dev] [PATCH v4 10/16] net/pcap: " Thomas Monjalon
2020-11-03 12:22   ` [dpdk-dev] [PATCH v4 11/16] app/testpmd: " Thomas Monjalon
2020-11-03 12:22   ` [dpdk-dev] [PATCH v4 12/16] examples/rxtx_callbacks: switch timestamp to dynamic field Thomas Monjalon
2020-11-03 12:22   ` [dpdk-dev] [PATCH v4 13/16] ethdev: add doxygen comment for Rx timestamp API Thomas Monjalon
2020-11-03 12:40     ` Andrew Rybchenko
2020-11-03 12:22   ` [dpdk-dev] [PATCH v4 14/16] mbuf: remove deprecated timestamp field Thomas Monjalon
2020-11-03 12:22   ` [dpdk-dev] [PATCH v4 15/16] mbuf: add Tx timestamp registration helper Thomas Monjalon
2020-11-03 12:42     ` Andrew Rybchenko
2020-11-03 12:22   ` [dpdk-dev] [PATCH v4 16/16] ethdev: include mbuf registration in Tx timestamp API Thomas Monjalon
2020-11-03 12:45     ` Andrew Rybchenko
2020-11-03 14:09 ` [dpdk-dev] [PATCH v5 00/16] remove mbuf timestamp Thomas Monjalon
2020-11-03 14:09   ` [dpdk-dev] [PATCH v5 01/16] eventdev: remove software Rx timestamp Thomas Monjalon
2020-11-03 14:09   ` [dpdk-dev] [PATCH v5 02/16] mbuf: add Rx timestamp flag and helpers Thomas Monjalon
2020-11-03 14:09   ` [dpdk-dev] [PATCH v5 03/16] latency: switch Rx timestamp to dynamic mbuf field Thomas Monjalon
2020-11-03 14:09   ` [dpdk-dev] [PATCH v5 04/16] net/ark: " Thomas Monjalon
2020-11-03 14:09   ` [dpdk-dev] [PATCH v5 05/16] net/dpaa2: " Thomas Monjalon
2020-11-03 14:09   ` [dpdk-dev] [PATCH v5 06/16] net/mlx5: fix dynamic mbuf offset lookup check Thomas Monjalon
2020-11-03 14:09   ` [dpdk-dev] [PATCH v5 07/16] net/mlx5: switch Rx timestamp to dynamic mbuf field Thomas Monjalon
2020-11-03 14:09   ` [dpdk-dev] [PATCH v5 08/16] net/nfb: " Thomas Monjalon
2020-11-03 14:09   ` [dpdk-dev] [PATCH v5 09/16] net/octeontx2: " Thomas Monjalon
2020-11-03 14:09   ` [dpdk-dev] [PATCH v5 10/16] net/pcap: " Thomas Monjalon
2020-11-03 14:09   ` [dpdk-dev] [PATCH v5 11/16] app/testpmd: " Thomas Monjalon
2020-11-03 14:09   ` [dpdk-dev] [PATCH v5 12/16] examples/rxtx_callbacks: switch timestamp to dynamic field Thomas Monjalon
2020-11-03 14:09   ` [dpdk-dev] [PATCH v5 13/16] ethdev: add doxygen comment for Rx timestamp API Thomas Monjalon
2020-11-03 19:07     ` Ajit Khaparde
2020-11-03 14:09   ` [dpdk-dev] [PATCH v5 14/16] mbuf: remove deprecated timestamp field Thomas Monjalon
2020-11-03 14:09   ` [dpdk-dev] [PATCH v5 15/16] mbuf: add Tx timestamp registration helper Thomas Monjalon
2020-11-03 14:09   ` [dpdk-dev] [PATCH v5 16/16] ethdev: include mbuf registration in Tx timestamp API Thomas Monjalon
2020-11-03 14:17   ` [dpdk-dev] [PATCH v5 00/16] remove mbuf timestamp Olivier Matz
2020-11-03 14:44     ` Thomas Monjalon
2020-11-03 16:08   ` Stephen Hemminger
2020-11-03 16:20     ` Thomas Monjalon
2020-11-03 17:42       ` Stephen Hemminger
2020-11-03 17:55         ` Thomas Monjalon

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