[ovs-dev] [PATCH v4 2/3] netdev-dpdk: Add custom stat for vhost tx retries.

[Ilya Maximets]

On 03.07.2019 18:03, Ian Stokes wrote:
> On 7/2/2019 1:32 AM, Kevin Traynor wrote:
>> vhost tx retries may occur, and it can be a sign that
>> the guest is not optimally configured.
>>
>> Add a custom stat so a user will know if vhost tx retries are
>> occurring and hence give a hint that guest config should be
>> examined.
>>
> 
> Thanks Kevin, tests ok for me.
> 
> Just a general comment on the design. In comparison to the previous approach proposed there seems to be more required with the custom stat approach below.
> 
> This may be ok as the retry is very OVS DPDK specific and doesn;t come dor lets say DPDK (unlike the XTATS).
> 
> @Ilya, whats your thoughts? Is this approach preferable for you rather than adding it to the general stats for all devices? (in which case I agree, they will not be used for dpdk types so will not be of use).

I think, It's better to keep this in custom stats section since
no other port types are going to use it in a near future.

Have a few style/naming comments inline.

> 
> One other minor comment below.
> 
>> Signed-off-by: Kevin Traynor <ktraynor at redhat.com>
>> ---
>>   Documentation/topics/dpdk/vhost-user.rst |  5 ++++
>>   lib/netdev-dpdk.c                        | 38 +++++++++++++++++++++++-
>>   2 files changed, 42 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/topics/dpdk/vhost-user.rst b/Documentation/topics/dpdk/vhost-user.rst
>> index 5f393aced..368f44520 100644
>> --- a/Documentation/topics/dpdk/vhost-user.rst
>> +++ b/Documentation/topics/dpdk/vhost-user.rst
>> @@ -521,4 +521,9 @@ The guest should also have sufficient cores dedicated for consuming and
>>   processing packets at the required rate.
>>   +The amount of Tx retries on a vhost-user or vhost-user-client interface can be
>> +shown with::
>> +
>> +  $ ovs-vsctl get Interface dpdkvhostclient0 statistics:tx_retries
>> +
>>   vhost-user Dequeue Zero Copy (experimental)
>>   -------------------------------------------
>> diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
>> index a380b6ffe..d3e02d389 100644
>> --- a/lib/netdev-dpdk.c
>> +++ b/lib/netdev-dpdk.c
>> @@ -139,4 +139,10 @@ BUILD_ASSERT_DECL((MAX_NB_MBUF / ROUND_DOWN_POW2(MAX_NB_MBUF / MIN_NB_MBUF))
>>   #define XSTAT_RX_JABBER_ERRORS           "rx_jabber_errors"
>>   +/* Size of vHost custom stats. */
>> +#define VHOST_STAT_TX_RETRIES_SIZE    1

I think, it's better to rename to something like VHOST_CUSTOM_STATS_SIZE.


>> +
>> +/* Name of vHost custom stats. */

s/Name/Names/ ?

>> +#define VHOST_STAT_TX_RETRIES    "tx_retries" > +
> 
> The alignment of the defines above look odd as they are not aligned with the existing DPDK XSTAT name definitions. It's only minor, as Kevin is on leave I think this will be ok to change on commit if there are no objections.

Sure.

> 
> Regards
> Ian
>>   #define SOCKET0              0
>>   @@ -434,7 +440,9 @@ struct netdev_dpdk {
>>       PADDED_MEMBERS(CACHE_LINE_SIZE,
>>           struct netdev_stats stats;
>> +        /* Custom stat for retries when unable to transmit. */
>> +        uint64_t tx_retries;
>>           /* Protects stats */
>>           rte_spinlock_t stats_lock;
>> -        /* 44 pad bytes here. */
>> +        /* 4 pad bytes here. */
>>       );
>>   @@ -1190,4 +1198,6 @@ common_construct(struct netdev *netdev, dpdk_port_t port_no,
>>       dev->rte_xstats_ids_size = 0;
>>   +    dev->tx_retries = 0;
>> +
>>       return 0;
>>   }
>> @@ -2381,4 +2391,5 @@ __netdev_dpdk_vhost_send(struct netdev *netdev, int qid,
>>       netdev_dpdk_vhost_update_tx_counters(&dev->stats, pkts, total_pkts,
>>                                            cnt + dropped);
>> +    dev->tx_retries += MIN(retries, VHOST_ENQ_RETRY_NUM);
>>       rte_spinlock_unlock(&dev->stats_lock);
>>   @@ -2818,4 +2829,27 @@ netdev_dpdk_get_custom_stats(const struct netdev *netdev,
>>   }
>>   +static int
>> +netdev_dpdk_vhost_get_custom_stats(const struct netdev *netdev,
>> +                                   struct netdev_custom_stats *custom_stats)
>> +{
>> +    struct netdev_dpdk *dev = netdev_dpdk_cast(netdev);
>> +
>> +    ovs_mutex_lock(&dev->mutex);
>> +
>> +    custom_stats->size = VHOST_STAT_TX_RETRIES_SIZE;
>> +    custom_stats->counters = (struct netdev_custom_counter *)
>> +                                 xzalloc(sizeof(struct netdev_custom_counter));

Since we have a _SIZE, we, probably, need to use it while allocation.
With this and a few coding-style fixes, this line should look like:

    custom_stats->counters = xcalloc(VHOST_STAT_TX_RETRIES_SIZE,
                                     sizeof *custom_stats->counters);

>> +    ovs_strlcpy(custom_stats->counters->name, VHOST_STAT_TX_RETRIES,
>> +                NETDEV_CUSTOM_STATS_NAME_SIZE);
>> +
>> +    rte_spinlock_lock(&dev->stats_lock);
>> +    custom_stats->counters->value = dev->tx_retries;
>> +    rte_spinlock_unlock(&dev->stats_lock);
>> +
>> +    ovs_mutex_unlock(&dev->mutex);
>> +
>> +    return 0;
>> +}
>> +
>>   static int
>>   netdev_dpdk_get_features(const struct netdev *netdev,
>> @@ -4398,4 +4432,5 @@ static const struct netdev_class dpdk_vhost_class = {
>>       .get_carrier = netdev_dpdk_vhost_get_carrier,
>>       .get_stats = netdev_dpdk_vhost_get_stats,
>> +    .get_custom_stats = netdev_dpdk_vhost_get_custom_stats,
>>       .get_status = netdev_dpdk_vhost_user_get_status,
>>       .reconfigure = netdev_dpdk_vhost_reconfigure,
>> @@ -4413,4 +4448,5 @@ static const struct netdev_class dpdk_vhost_client_class = {
>>       .get_carrier = netdev_dpdk_vhost_get_carrier,
>>       .get_stats = netdev_dpdk_vhost_get_stats,
>> +    .get_custom_stats = netdev_dpdk_vhost_get_custom_stats,
>>       .get_status = netdev_dpdk_vhost_user_get_status,
>>       .reconfigure = netdev_dpdk_vhost_client_reconfigure,
>>