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mbuf: add function to reset headroom

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Some application use rte_mbuf_raw_alloc() function to improve
performance by not resetting mbuf's fields to their default state.

This can be however problematic for mbuf consumers that need some
headroom, meaning that data_off field gets decremented after
allocation. When the mbuf is re-used afterwards, there might not
be enough room for the consumer to prepend anything, if the data_off
field is not reset to its default value.

This patch adds a new rte_pktmbuf_reset_headroom() function that
applications can call to reset the data_off field.
This patch also replaces current data_off affectations in the mbuf
lib with a call to this function.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>
This commit is contained in:
Maxime Coquelin 2016-10-04 14:05:23 +02:00 committed by Thomas Monjalon
parent 4e8739e9bb
commit febf2bb46d
1 changed files with 15 additions and 3 deletions
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18
lib/librte_mbuf/rte_mbuf.h
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@ -1386,6 +1386,19 @@ rte_pktmbuf_priv_size(struct rte_mempool *mp)
return mbp_priv->mbuf_priv_size;
}
/**
* Reset the data_off field of a packet mbuf to its default value.
*
* The given mbuf must have only one segment, which should be empty.
*
* @param m
* The packet mbuf's data_off field has to be reset.
*/
static inline void rte_pktmbuf_reset_headroom(struct rte_mbuf *m)
{
m->data_off = RTE_MIN(RTE_PKTMBUF_HEADROOM, (uint16_t)m->buf_len);
}
/**
* Reset the fields of a packet mbuf to their default values.
*
@ -1406,8 +1419,7 @@ static inline void rte_pktmbuf_reset(struct rte_mbuf *m)
m->ol_flags = 0;
m->packet_type = 0;
m->data_off = (RTE_PKTMBUF_HEADROOM <= m->buf_len) ?
RTE_PKTMBUF_HEADROOM : m->buf_len;
rte_pktmbuf_reset_headroom(m);
m->data_len = 0;
__rte_mbuf_sanity_check(m, 1);
@ -1571,7 +1583,7 @@ static inline void rte_pktmbuf_detach(struct rte_mbuf *m)
m->buf_addr = (char *)m + mbuf_size;
m->buf_physaddr = rte_mempool_virt2phy(mp, m) + mbuf_size;
m->buf_len = (uint16_t)buf_len;
m->data_off = RTE_MIN(RTE_PKTMBUF_HEADROOM, (uint16_t)m->buf_len);
rte_pktmbuf_reset_headroom(m);
m->data_len = 0;
m->ol_flags = 0;