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Subject: mbuf headroom question
Date: Thu, 6 Jan 2022 10:29:11 +0100
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Thread-Topic: mbuf headroom question
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From: =?iso-8859-1?Q?Morten_Br=F8rup?= <mb@smartsharesystems.com>
To: "Olivier Matz" <olivier.matz@6wind.com>,
	<dev@dpdk.org>
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Hi Olivier,

The data_room_size parameter description for the mbuf pool creation =
functions says:
"Size of data buffer in each mbuf, including RTE_PKTMBUF_HEADROOM."

Furthermore, both rte_mbuf_data_iova_default() and =
rte_mbuf_data_addr_default() simply add RTE_PKTMBUF_HEADROOM to the =
return value.

Based on the above, I would think that it is impossible for m->buf_len =
to be smaller than RTE_PKTMBUF_HEADROOM.

So why does rte_pktmbuf_reset_headroom() use RTE_MIN(m->buf_len, =
RTE_PKTMBUF_HEADROOM), instead of just RTE_PKTMBUF_HEADROOM? What am I =
missing here?


Med venlig hilsen / Kind regards,
-Morten Br=F8rup