> -----Original Message----- > From: Jean-Mickael Guerin [mailto:jean-mickael.guerin at 6wind.com] > Sent: Friday, December 05, 2014 4:59 PM > To: Ananyev, Konstantin > Cc: dev at dpdk.org > Subject: Re: [dpdk-dev] [RFC PATCH] ixgbe: ixgbe_recv_pkts_vec shouldn't > override mbuf buffer length > > On 05/12/2014 16:20, Konstantin Ananyev wrote: > > That's an alternative way to fix the problem described in the patch: > > http://dpdk.org/ml/archives/dev/2014-December/009394.html. > > The main difference is: > > - move buf_len fields out of rearm_data marker. > > - make ixgbe_recv_pkts_vec() not touch buf_len field at all > > (as all other RX functions behave). > > > > Signed-off-by: Konstantin Ananyev <konstantin.ananyev at intel.com> > > --- > > lib/librte_mbuf/rte_mbuf.h | 7 +++++-- > > lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c | 20 +++++++++++++++----- > > 2 files changed, 20 insertions(+), 7 deletions(-) > > > > diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h > > index 2e5fce5..bb88318 100644 > > --- a/lib/librte_mbuf/rte_mbuf.h > > +++ b/lib/librte_mbuf/rte_mbuf.h > > @@ -179,6 +179,8 @@ const char *rte_get_tx_ol_flag_name(uint64_t mask); > > typedef void *MARKER[0]; /**< generic marker for a point in a > > structure */ > > typedef uint64_t MARKER64[0]; /**< marker that allows us to overwrite 8 > > bytes > > * with a single assignment */ > > +typedef uint8_t MARKER8[0]; /**< generic marker with 1B alignment */ > > + > > /** > > * The generic rte_mbuf, containing a packet mbuf. > > */ > > @@ -188,9 +190,10 @@ struct rte_mbuf { > > void *buf_addr; /**< Virtual address of segment buffer. */ > > phys_addr_t buf_physaddr; /**< Physical address of segment buffer. */ > > > > - /* next 8 bytes are initialised on RX descriptor rearm */ > > - MARKER64 rearm_data; > > uint16_t buf_len; /**< Length of segment buffer. */ > > + > > + /* next 6 bytes are initialised on RX descriptor rearm */ > > + MARKER8 rearm_data; > > uint16_t data_off; > > > > /** > > diff --git a/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c > > b/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c > > index 579bc46..d5fc0cc 100644 > > --- a/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c > > +++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx_vec.c > > @@ -79,13 +79,22 @@ ixgbe_rxq_rearm(struct igb_rx_queue *rxq) > > /* Initialize the mbufs in vector, process 2 mbufs in one loop */ > > for (i = 0; i < RTE_IXGBE_RXQ_REARM_THRESH; i += 2, rxep += 2) { > > __m128i vaddr0, vaddr1; > > + uintptr_t p0, p1; > > > > mb0 = rxep[0].mbuf; > > mb1 = rxep[1].mbuf; > > > > - /* flush mbuf with pkt template */ > > - mb0->rearm_data[0] = rxq->mbuf_initializer; > > - mb1->rearm_data[0] = rxq->mbuf_initializer; > > + /* > > + * Flush mbuf with pkt template. > > + * Data to be rearmed is 6 bytes long. > > + * Though, RX will overwrite ol_flags that are coming next > > + * anyway. So overwrite whole 8 bytes with one load: > > + * 6 bytes of rearm_data plus first 2 bytes of ol_flags. > > + */ > > + p0 = (uintptr_t)&mb0->rearm_data; > > + *(uint64_t *)p0 = rxq->mbuf_initializer; > > + p1 = (uintptr_t)&mb1->rearm_data; > > + *(uint64_t *)p1 = rxq->mbuf_initializer; > > > > /* load buf_addr(lo 64bit) and buf_physaddr(hi 64bit) */ > > vaddr0 = _mm_loadu_si128((__m128i *)&(mb0->buf_addr)); > > @@ -732,14 +741,15 @@ static struct ixgbe_txq_ops vec_txq_ops = { > > int > > ixgbe_rxq_vec_setup(struct igb_rx_queue *rxq) > > { > > + uintptr_t p; > > struct rte_mbuf mb_def = { .buf_addr = 0 }; /* zeroed mbuf */ > > > > mb_def.nb_segs = 1; > > mb_def.data_off = RTE_PKTMBUF_HEADROOM; > > - mb_def.buf_len = rxq->mb_pool->elt_size - sizeof(struct rte_mbuf); > > mb_def.port = rxq->port_id; > > rte_mbuf_refcnt_set(&mb_def, 1); > > - rxq->mbuf_initializer = *((uint64_t *)&mb_def.rearm_data); > > + p = (uintptr_t)&mb_def.rearm_data; > > + rxq->mbuf_initializer = *(uint64_t *)p; > > return 0; > > } > > > > > > The patch introduces writes on unaligned data, but we can assume no > performance penalty on intel hw, correct? >
Yes to both: it introduces 64bit unaligned store. I run performance test on IVB board, didn't see any degradation. Konstantin
