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From: David Marchand <david.marchand@redhat.com>
To: Olivier Matz <olivier.matz@6wind.com>, Ali Alnubani <alialnu@nvidia.com>
Cc: dev <dev@dpdk.org>,
	Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>,
	 "Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
	Morten Brørup <mb@smartsharesystems.com>,
	 ajitkhaparde@gmail.com, dpdk stable <stable@dpdk.org>,
	 Ajit Khaparde <ajit.khaparde@broadcom.com>
Subject: Re: [dpdk-stable] [PATCH v4] mbuf: fix reset on mbuf free
Date: Fri, 15 Jan 2021 14:59:52 +0100
Message-ID: <CAJFAV8zDhz_5nhk9Q1TPvWOoq+Zw9pi2uSC3_cB9TaAo6bhgaw@mail.gmail.com> (raw)
In-Reply-To: <20210113132734.1636-1-olivier.matz@6wind.com>

On Wed, Jan 13, 2021 at 2:28 PM Olivier Matz <olivier.matz@6wind.com> wrote:
>
> m->nb_seg must be reset on mbuf free whatever the value of m->next,
> because it can happen that m->nb_seg is != 1. For instance in this
> case:
>
>   m1 = rte_pktmbuf_alloc(mp);
>   rte_pktmbuf_append(m1, 500);
>   m2 = rte_pktmbuf_alloc(mp);
>   rte_pktmbuf_append(m2, 500);
>   rte_pktmbuf_chain(m1, m2);
>   m0 = rte_pktmbuf_alloc(mp);
>   rte_pktmbuf_append(m0, 500);
>   rte_pktmbuf_chain(m0, m1);
>
> As rte_pktmbuf_chain() does not reset nb_seg in the initial m1
> segment (this is not required), after this code the mbuf chain
> have 3 segments:
>   - m0: next=m1, nb_seg=3
>   - m1: next=m2, nb_seg=2
>   - m2: next=NULL, nb_seg=1
>
> Then split this chain between m1 and m2, it would result in 2 packets:
>   - first packet
>     - m0: next=m1, nb_seg=2
>     - m1: next=NULL, nb_seg=2
>   - second packet
>     - m2: next=NULL, nb_seg=1
>
> Freeing the first packet will not restore nb_seg=1 in the second
> segment. This is an issue because it is expected that mbufs stored
> in pool have their nb_seg field set to 1.
>
> Fixes: 8f094a9ac5d7 ("mbuf: set mbuf fields while in pool")
> Cc: stable@dpdk.org
>
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> Acked-by: Morten Brørup <mb@smartsharesystems.com>
> Acked-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
> Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
> ---
>
> v4
> * add a unit test (suggested by David)

Olivier,

Thanks, for adding it.


Ali,

You reported some performance regression, did you confirm it?
If I get no reply by monday, I'll proceed with this patch.


Thanks.
-- 
David Marchand


  reply	other threads:[~2021-01-15 14:00 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-04 17:00 [dpdk-stable] [PATCH] " Olivier Matz
2020-11-05  0:15 ` Ananyev, Konstantin
2020-11-05  7:46   ` Olivier Matz
2020-11-05  8:33     ` [dpdk-stable] [dpdk-dev] " Morten Brørup
2020-11-05  9:03       ` Olivier Matz
2020-11-05  9:09     ` Andrew Rybchenko
2020-11-08  7:25 ` Ali Alnubani
2020-12-18 12:52 ` [dpdk-stable] [PATCH v2] " Olivier Matz
2020-12-18 13:18   ` [dpdk-stable] [dpdk-dev] " Morten Brørup
2020-12-18 23:33     ` Ajit Khaparde
2021-01-06 13:33 ` [dpdk-stable] [PATCH v3] " Olivier Matz
2021-01-10  9:28   ` Ali Alnubani
2021-01-11 13:14   ` Ananyev, Konstantin
2021-01-13 13:27 ` [dpdk-stable] [PATCH v4] " Olivier Matz
2021-01-15 13:59   ` David Marchand [this message]
2021-01-15 18:39     ` Ali Alnubani
2021-01-18 17:52       ` Ali Alnubani
2021-01-19  8:32         ` Olivier Matz
2021-01-19  8:53           ` Morten Brørup
2021-01-19 12:00             ` Ferruh Yigit
2021-01-19 12:27               ` [dpdk-stable] [dpdk-dev] " Morten Brørup
2021-01-19 14:03                 ` Ferruh Yigit
2021-01-19 14:21                   ` Morten Brørup
2021-01-21  9:15                     ` Ferruh Yigit
2021-01-19 14:04           ` [dpdk-stable] " Slava Ovsiienko
2021-07-24  8:47             ` [dpdk-stable] [dpdk-dev] " Thomas Monjalon
2021-07-30 12:36               ` Olivier Matz
2021-07-30 14:35                 ` Morten Brørup
2021-07-30 14:54                   ` Thomas Monjalon
2021-07-30 15:14                     ` Olivier Matz
2021-07-30 15:23                       ` Morten Brørup
2021-01-21  9:19       ` [dpdk-stable] " Ferruh Yigit
2021-01-21  9:29         ` [dpdk-stable] [dpdk-dev] " Morten Brørup
2021-01-21 16:35           ` [dpdk-stable] [dpdklab] " Lincoln Lavoie
2021-01-23  8:57             ` [dpdk-stable] [dpdk-dev] [dpdklab] " Morten Brørup
2021-01-25 17:00               ` Brandon Lo
2021-01-25 18:42             ` [dpdk-stable] [dpdklab] RE: [dpdk-dev] " Ferruh Yigit
2021-06-15 13:56   ` [dpdk-stable] " Morten Brørup

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