Hi, Panu:
> -----Original Message-----
> From: Panu Matilainen [mailto:pmatilai at redhat.com]
> Sent: Monday, August 22, 2016 3:53 PM
> To: Yang, Zhiyong <zhiyong.yang at intel.com>; dev at dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] vhost: add pmd xstats
>
> On 08/19/2016 03:16 PM, Zhiyong Yang wrote:
> > This feature adds vhost pmd extended statistics from per queue
> > perspective for the application such as OVS etc.
> >
> > The statistics counters are based on RFC 2819 and 2863 as follows:
> >
> > rx/tx_good_packets
> > rx/tx_total_bytes
> > rx/tx_dropped_pkts
> > rx/tx_broadcast_packets
> > rx/tx_multicast_packets
> > rx/tx_ucast_packets
> > rx/tx_undersize_errors
> > rx/tx_size_64_packets
> > rx/tx_size_65_to_127_packets;
> > rx/tx_size_128_to_255_packets;
> > rx/tx_size_256_to_511_packets;
> > rx/tx_size_512_to_1023_packets;
> > rx/tx_size_1024_to_1522_packets;
> > rx/tx_1523_to_max_packets;
> > rx/tx_errors
> > rx_fragmented_errors
> > rx_jabber_errors
> > rx_unknown_protos_packets;
> >
> > No API is changed or added.
> > rte_eth_xstats_get_names() to retrieve what kinds of vhost xstats are
> > supported,
> > rte_eth_xstats_get() to retrieve vhost extended statistics,
> > rte_eth_xstats_reset() to reset vhost extended statistics.
> >
> > Since collecting data of vhost_update_packet_xstats will have some
> > effect on RX/TX performance, so, Setting compiling switch
> > CONFIG_RTE_LIBRTE_PMD_VHOST_UPDATE_XSTATS=n by default in the
> file
> > config/common_base, if needing xstats data, you can enable it(y).
>
> NAK, such things need to be switchable at run-time.
>
> - Panu -
Considering the following reasons using the compiler switch, not
command-line at run-time.
1.Similar xstats update functions are always collecting stats data in the
background when rx/tx are running, such as the physical NIC or virtio,
which have no switch. Compiler switch for vhost pmd xstats is added
as a option when performance is viewed as critical factor.
2. No data structure and API in any layer support the xstats update switch
at run-time. Common data structure (struct rte_eth_dev_data) has no
device-specific data member, if implementing enable/disable of vhost_update
_packet_xstats at run-time, must define a flag(device-specific) in it,
because the definition of struct vhost_queue in the driver code
(eth_vhost_rx/eth_vhost_tx processing)is not visible from device perspective.
3. I tested RX/TX with v1 patch (y) as reference based on Intel(R)
Xeon(R) CPU E5-2699 v3 @ 2.30GHz, for 64byts packets in burst mode, 32 packets
in one RX/TX processing. Overhead of vhost_update_packet_xstats is less than
3% for the rx/tx processing. It looks that vhost_update_packet_xstats has a
limited effect on performance drop.
-zhiyong-
