Hi Konstantin, On 04/28/2015 03:02 PM, Konstantin Ananyev wrote: > Latest mbuf changes (priv_size addition and related fixes) > exposed small problem with testpmd default config: > testpmd default mbuf size is exaclty 2KB, that causes > ixgbe PMD to select scattered RX even for configs with 'normal' > max packet length (max_rx_pkt_len == ETHER_MAX_LEN). > > Signed-off-by: Konstantin Ananyev <konstantin.ananyev at intel.com> > --- > app/test-pmd/testpmd.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/app/test-pmd/testpmd.h b/app/test-pmd/testpmd.h > index 389fc24..037e7ec 100644 > --- a/app/test-pmd/testpmd.h > +++ b/app/test-pmd/testpmd.h > @@ -48,7 +48,8 @@ > * Default size of the mbuf data buffer to receive standard 1518-byte > * Ethernet frames in a mono-segment memory buffer. > */ > -#define DEFAULT_MBUF_DATA_SIZE 2048 /**< Default size of mbuf data buffer. */ > +#define DEFAULT_MBUF_DATA_SIZE (2048 + RTE_PKTMBUF_HEADROOM) > +/**< Default size of mbuf data buffer. */ > > /* > * The maximum number of segments per packet is used when creating >
Indeed, this regression is introduced by one of my recent patch: http://dpdk.org/browse/dpdk/commit/?id=dfb03bbe2b39156f0e42e7f29e09c1e6b6def265 Before, m->buf_len was initialized to RTE_PKTMBUF_HEADROOM + 2048. Now it is set to 2048. Maybe a line like this should be added in the commit log: Fixes: dfb03bbe2b ("app/testpmd: use standard functions to initialize mbufs and mbuf pool") Just one question Konstantin: could you just confirm that the reason of the bug? From what I understand: - buf_len is 2048 - the rx data size when receiving a packet is 2048 - hdroom = 1920 - at init, the ixgbe driver configures the hw to set the max rx data size, but it has to be a power of 2, so 1024 is chosen - then the initialization code check if a packet of ETHER_MAX_LEN fits in max rx size, and if not, it selects the scatter mode. It makes me wondering 2 things: - should we add a comment in the test-pmd to explain that? (maybe not, as it is driver-specific, and it is just an optimization) - should we check the other examples to see if the same problem exists? If my understanding is correct, Acked-by: Olivier Matz <olivier.matz at 6wind.com> Regards, Olivier
