Hi,  Panu:

-----Original Message-----
From: Panu Matilainen [mailto:pmatilai@redhat.com]
Sent: Monday, August 22, 2016 3:53 PM
To: Yang, Zhiyong <redacted>; dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] vhost: add pmd xstats

On 08/19/2016 03:16 PM, Zhiyong Yang wrote:

quoted

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

quoted

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-