From: "Morten Brørup" <mb@smartsharesystems.com>
To: "Slava Ovsiienko" <viacheslavo@nvidia.com>,
"NBU-Contact-Thomas Monjalon" <thomas@monjalon.net>,
<dev@dpdk.org>, <techboard@dpdk.org>
Cc: "Ajit Khaparde" <ajit.khaparde@broadcom.com>,
"Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
"Andrew Rybchenko" <andrew.rybchenko@oktetlabs.ru>,
<dev@dpdk.org>, "Yigit, Ferruh" <ferruh.yigit@intel.com>,
<david.marchand@redhat.com>,
"Richardson, Bruce" <bruce.richardson@intel.com>,
<olivier.matz@6wind.com>, <jerinj@marvell.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 16:03:46 +0100 [thread overview]
Message-ID: <98CBD80474FA8B44BF855DF32C47DC35C613DF@smartserver.smartshare.dk> (raw)
In-Reply-To: <MWHPR12MB150109404B0B68CD9D70B4A6DF110@MWHPR12MB1501.namprd12.prod.outlook.com>
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Slava Ovsiienko
> Sent: Tuesday, November 3, 2020 3:03 PM
>
> Hi, Morten
>
> > From: Morten Brørup <mb@smartsharesystems.com>
> > Sent: Tuesday, November 3, 2020 14:10
> >
> > > 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.
> Not all PMDs use this field on Tx. HW might support the checksum
> offloads
> directly, not requiring these fields at all.
>
>
> > 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.
> 256 mpool looks enough, as for me. Regarding the indirect access to the
> pool
> (via some table) - it might introduce some performance impact.
It might, but I hope that it is negligible, so the benefits outweigh the disadvantages.
It would have to be measured, though.
And m->pool is only used for free()'ing (and detach()'ing) mbufs.
> For example,
> mlx5 PMD strongly relies on pool field for allocating mbufs in Rx
> datapath.
> We're going to update (o-o, we found point to optimize), but for now it
> does.
Without looking at the source code, I don't think the PMD is using m->pool in the RX datapath, I think it is using a pool dedicated to a receive queue used for RX descriptors in the PMD (i.e. driver->queue->pool).
>
> > 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;
> > }
>
> Sorry, not sure about this. IIRC, nb_segs is valid in the first
> segment/mbuf only.
> If we have the 4 segments in the pkt we see nb_seg=4 in the first one,
> and the nb_seg=1
> in the others. The next field is NULL in the last mbuf only. Am I wrong
> and miss something ?
You are correct.
This would have to be updated too. Either by increasing m->nb_seg in the following segments, or by splitting up relevant functions into functions for working on first segments (incl. non-segmented packets), and functions for working on following segments of segmented packets.
>
> > 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.
> >
> > (I guess that regression testing didn't catch this because the tests
> perform TX
> > immediately after RX, so the cache miss just moves from the TX to the
> RX part
> > of the test application.)
> >
> >
> > 2. Regarding short term goals:
> >
> > The current DPDK source code looks to me like m->next is the most
> frequently
> > accessed field in the second cache line, so it makes sense moving
> this to the
> > first cache line, rather than m->pool.
> > Benchmarking may help here.
>
> Moreover, for the segmented packets the packet size is supposed to be
> large,
> and it imposes the relatively low packet rate, so probably optimization
> of
> moving next to the 1st cache line might be negligible at all. Just
> compare 148Mpps of
> 64B pkts and 4Mpps of 3000B pkts over 100Gbps link. Currently we are on
> benchmarking
> and did not succeed yet on difference finding. The benefit can't be
> expressed in mpps delta,
> we should measure CPU clocks, but Rx queue is almost always empty - we
> have an empty
> loops. So, if we have the boost - it is extremely hard to catch one.
Very good point regarding the value of such an optimization, Slava!
And when free()'ing packets, both m->next and m->pool are touched.
So perhaps the free()/detach() functions in the mbuf library can be modified to handle first segments (and non-segmented packets) and following segments differently, so accessing m->next can be avoided for non-segmented packets. Then m->pool should be moved to the first cache line.
next prev parent reply other threads:[~2020-11-03 15:03 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
2020-11-03 14:03 ` Morten Brørup
2020-11-03 14:02 ` Slava Ovsiienko
2020-11-03 15:03 ` Morten Brørup [this message]
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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