From: Bruce Richardson <bruce.richardson@intel.com>
To: Olivier MATZ <olivier.matz@6wind.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH 2/2] Remove RTE_MBUF_REFCNT references
Date: Wed, 18 Feb 2015 09:35:50 +0000 [thread overview]
Message-ID: <20150218093548.GA14884@bricha3-MOBL3> (raw)
In-Reply-To: <54E45888.7070603@6wind.com>
On Wed, Feb 18, 2015 at 10:16:56AM +0100, Olivier MATZ wrote:
> Hi Sergio,
>
> On 02/16/2015 05:08 PM, Sergio Gonzalez Monroy wrote:
> >This patch removes all references to RTE_MBUF_REFCNT, setting the refcnt
> >field in the mbuf struct permanently.
> >
> >Signed-off-by: Sergio Gonzalez Monroy <sergio.gonzalez.monroy@intel.com>
>
> I think removing the refcount compile option goes in the right
> direction. However, activating the refcount will break the applications
> that reserve a private zone in mbufs. This is due to the macros
> RTE_MBUF_TO_BADDR() and RTE_MBUF_FROM_BADDR() that suppose that
> the beginning of the mbuf is 128 bytes (sizeof mbuf) before the
> data buffer.
>
While I understand how the macros make certain assumptions, how does activating
the refcnt specifically lead to the problems you describe? Could you explain
that part in a bit more detail?
Thanks,
/Bruce
> For RTE_MBUF_TO_BADDR(), it's relatively easy to replace it. The
> mbuf pool could store the size of the private size like it's done
> for mbp_priv->mbuf_data_room_size. Using rte_mempool_from_obj(m)
> or m->pool, we can retrieve the mbuf pool and this value, then
> compute the buffer address.
>
> For RTE_MBUF_FROM_BADDR(), it's more complex. We could ensure that
> a backpointer to the mbuf is always located before the data buffer,
> but it looks difficult to do.
>
> Another idea would be to add a field in indirect mbufs that stores
> the pointer to the "parent" mbuf.
>
> Regards,
> Olivier
>
next prev parent reply other threads:[~2015-02-18 9:35 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-16 16:08 [dpdk-dev] [PATCH 0/2] Removal of RTE_MBUF_REFCNT Sergio Gonzalez Monroy
2015-02-16 16:08 ` [dpdk-dev] [PATCH 1/2] mbuf: Introduce IND_ATTACHED_MBUF flag Sergio Gonzalez Monroy
2015-02-16 16:08 ` [dpdk-dev] [PATCH 2/2] Remove RTE_MBUF_REFCNT references Sergio Gonzalez Monroy
2015-02-18 9:16 ` Olivier MATZ
2015-02-18 9:35 ` Bruce Richardson [this message]
2015-02-18 9:48 ` Ananyev, Konstantin
2015-02-18 10:00 ` Bruce Richardson
2015-02-18 10:14 ` Olivier MATZ
2015-02-18 10:22 ` Ananyev, Konstantin
2015-02-18 10:22 ` Bruce Richardson
2015-02-18 10:33 ` Olivier MATZ
2015-02-18 10:37 ` Bruce Richardson
2015-02-18 10:47 ` Olivier MATZ
2015-02-18 10:47 ` Ananyev, Konstantin
2015-02-18 11:01 ` Olivier MATZ
2015-02-18 9:52 ` Olivier MATZ
2015-02-16 20:47 ` [dpdk-dev] [PATCH 0/2] Removal of RTE_MBUF_REFCNT Stephen Hemminger
2015-02-17 8:43 ` Gonzalez Monroy, Sergio
2015-02-18 11:03 ` [dpdk-dev] [PATCH v2 " Sergio Gonzalez Monroy
2015-02-18 11:03 ` [dpdk-dev] [PATCH v2 1/2] mbuf: Introduce IND_ATTACHED_MBUF flag Sergio Gonzalez Monroy
2015-02-18 11:03 ` [dpdk-dev] [PATCH v2 2/2] Remove RTE_MBUF_REFCNT references Sergio Gonzalez Monroy
2015-02-18 12:05 ` [dpdk-dev] [PATCH v2 0/2] Removal of RTE_MBUF_REFCNT Ananyev, Konstantin
2015-02-23 18:36 ` Thomas Monjalon
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