ping On 24.07.2015 15:59, Zoltan Kiss wrote: > Hi, > > On 24/07/15 11:13, Ciprian Barbu wrote: >> From: Ciprian Barbu <ciprian.barbu at enea.com> >> >> This tries to show an approximate behavior described in an earlier >> discussion >> called "can eth_igb_xmit_pkts called with len 0 affect transmission?" >> >> I'm using Intel i350 dual port 1Gb card and I've tweaked the pool size >> to the >> minimum possible. But unmodified l2fwd still worked withouth a sweat. >> After >> applying this patch transmission stopped after maybe 30 seconds. >> Lowering the >> 'magic' number causes l2fwd to stop sending packets even earlier. >> Using gdb I could see eth_igb_xmit_pkts always returning because nb_tx >> was 0 >> and E1000_TXD_STAT_DD was not set (approx igb_rxtx.c : 476) > > I think the proper solution for this will be to introduce an explicit > API which makes it possible for the application to call the actual PMD's > callback function, which flushes out the completed buffers from the TX > ring, if possible. Then in case of igb it could be a noop. See the > discussion in this thread:
What I' trying to show here is an unexpected behavior in the tx routine of the igb pmd. The documentation doesn't mention that making this call with 0 nb_pkt can cause undefined behavior. It would be nice if someone could take a look at this. > > http://dpdk.org/ml/archives/dev/2015-June/018487.html > > I'll plan to propose such API, but it won't be in the very near future, > as 2.1 will come out soon and no new features accepted at the moment. > For the short term we can introduce a check in ODP-DPDK, which avoids > this rte_eth_tx_burst(..., 0) call if the PMD is igb. How about that? > > >> >> Signed-off-by: Ciprian Barbu <ciprian.barbu at enea.com> >> --- >> examples/l2fwd/main.c | 13 +++++++++++-- >> 1 file changed, 11 insertions(+), 2 deletions(-) >> >> diff --git a/examples/l2fwd/main.c b/examples/l2fwd/main.c >> index 17621ee..623b836 100644 >> --- a/examples/l2fwd/main.c >> +++ b/examples/l2fwd/main.c >> @@ -72,7 +72,7 @@ >> #define RTE_LOGTYPE_L2FWD RTE_LOGTYPE_USER1 >> >> #define MBUF_SIZE (2048 + sizeof(struct rte_mbuf) + >> RTE_PKTMBUF_HEADROOM) >> -#define NB_MBUF 8192 >> +#define NB_MBUF 1024 >> >> #define MAX_PKT_BURST 32 >> #define BURST_TX_DRAIN_US 100 /* TX drain every ~100us */ >> @@ -260,7 +260,7 @@ l2fwd_main_loop(void) >> struct rte_mbuf *m; >> unsigned lcore_id; >> uint64_t prev_tsc, diff_tsc, cur_tsc, timer_tsc; >> - unsigned i, j, portid, nb_rx; >> + unsigned i, j, portid, nb_rx, magic = 0; >> struct lcore_queue_conf *qconf; >> const uint64_t drain_tsc = (rte_get_tsc_hz() + US_PER_S - 1) / >> US_PER_S * BURST_TX_DRAIN_US; >> >> @@ -285,6 +285,15 @@ l2fwd_main_loop(void) >> } >> >> while (1) { >> + if (++magic == 50000) { >> + magic = 0; >> + l2fwd_send_burst(&lcore_queue_conf[lcore_id], >> + 0, >> + (uint8_t) 0); >> + l2fwd_send_burst(&lcore_queue_conf[lcore_id], >> + 0, >> + (uint8_t) 1); >> + } >> >> cur_tsc = rte_rdtsc(); >> >>
