Hi Hanoch,
On Thu, Mar 22, 2018 at 10:00:45AM +0000, Hanoch Haim (hhaim) wrote:
> Hi Nelio,
>
> Let me provide more background.
> The context is TRex running in Advance Stateful (ASTf) mode using multi-core.
>
> In this case the flows are distributed using RSS. New flows (c->s)
> need to have a tuple that will match the generated core. For this
> calculation there is a need of to know the *RETA table size*
>
>
> Code:
>
> /*1. verify that driver can support RSS */
> rte_eth_dev_info_get(m_repid,&dev_info);
> save_reta_size = dev_info.reta_size
> save_hash_key = dev_info.hash_key_size
> printf("RETA_SIZE : %d \n",save_reta_size);
> printf("HASH_SIZE : %d \n",save_hash_key);
>
> /*2. configure queues */
> ret = rte_eth_dev_configure(m_repid,
> nb_rx_queue,
> nb_tx_queue,
> eth_conf);
> ..
>
> /* 3. reading the RETA again */
> rte_eth_dev_info_get(m_repid,&dev_info);
> save_reta_size = dev_info.reta_size <<
> save_hash_key = dev_info.hash_key_size
> printf("RETA_SIZE1 : %d \n",save_reta_size);
>
>
> /* 4. update the RETA table */
> rte_eth_dev_rss_reta_update(m_repid, &reta_conf[0], dev_info.reta_size)
>
>
> 2. /*Output in case of Intel i40e*/
>
> RETA_SIZE : 512
> HASH_SIZE : 52
>
> RETA_SIZE1 : 512
>
> 3. /*Output in case of Mlx5 */
>
> RETA_SIZE : 512
> HASH_SIZE : 0
>
> RETA_SIZE1 : 4 << not round of 64 , depends on the number of rx queues
Your need is to have a fixed size returned by the
rte_eth_dev_info_get(), the PMD can have an internal dynamic size, it
won't modify your spreading.
An information, you are getting the hash key size, according to the
documentation of struct rte_eth_rss_conf, only the i40e can have a key
len different from 40 bytes, others should just ignore the field [1].
Regards,
[1] https://dpdk.org/browse/dpdk/tree/lib/librte_ether/rte_ethdev.h#n380
> Hanoh
>
> -----Original Message-----
> From: Nélio Laranjeiro [mailto:nelio.laranje...@6wind.com]
> Sent: Thursday, March 22, 2018 11:28 AM
> To: Hanoch Haim (hhaim)
> Cc: Yongseok Koh; dev@dpdk.org
> Subject: Re: [dpdk-dev] mlx5 reta size is dynamic
>
> Hi Hanoch,
>
> On Thu, Mar 22, 2018 at 09:02:19AM +0000, Hanoch Haim (hhaim) wrote:
> > Hi Nelio,
> > I think you didn't understand me. I suggest to keep the RETA table
> > size constant (maximum 512 in your case) and don't change its base on
> > the number of configured Rx-queue.
>
> It is even simpler, we can return the maximum size or a multiple of
> RTE_RETA_GROUP_SIZE according to the number of Rx queues being used, in the
> devop->dev_infos_get() as it is what the
> rte_eth_dev_rss_reta_update() implementation will expect.
>
> > This will make the DPDK API consistent. As a user I need to do tricks
> > (allocate an odd/prime number of rx-queues) to get the RETA size
> > constant at 512
>
> I understand this issue, what I don't fully understand your needs.
>
> > I'm not talking about changing the values in the RETA table which can
> > be done while there is traffic.
>
> On MLX5 changing the entries of the RETA table don't affect the current
> traffic, it needs a port restart to affect it and only for "default"
> flows, any flow created through the public flow API are not impacted by the
> RETA table.
>
>
> From my understanding, you wish to have a size returned by
> devop->dev_infos_get() usable directly by rte_eth_dev_rss_reta_update().
> This is why you are asking for a fix size? So, if internally the PMD starts
> with a smaller RETA table does not really matter, until the RETA API works
> without any trick from the application side. Is this correct?
>
> Thanks,
>
> > Thanks,
> > Hanoh
> >
> >
> > -----Original Message-----
> > From: Nélio Laranjeiro [mailto:nelio.laranje...@6wind.com]
> > Sent: Thursday, March 22, 2018 10:55 AM
> > To: Hanoch Haim (hhaim)
> > Cc: Yongseok Koh; dev@dpdk.org
> > Subject: Re: [dpdk-dev] mlx5 reta size is dynamic
> >
> > On Thu, Mar 22, 2018 at 06:52:53AM +0000, Hanoch Haim (hhaim) wrote:
> > > Hi Yongseok,
> > >
> > >
> > > RSS has a DPDK API,application can ask for the reta table size and
> > > configure it. In your case you are assuming specific use case and
> > > change the size dynamically which solve 90% of the use-cases but
> > > break the 10% use-case.
> > > Instead, you could provide the application a consistent API and with
> > > that 100% of the applications can work with no issue. This is what
> > > happen with Intel (ixgbe/i40e) Another minor issue the rss_key_size
> > > return as zero but internally it is 40 bytes
> >
> > Hi Hanoch,
> >
> > Legacy DPDK API has always considered there is only a single indirection
> > table aka. RETA whereas this is not true [1][2] on this device.
> >
> > On MLX5 there is an indirection table per Hash Rx queue according to the
> > list of queues making part of it.
> > The Hash Rx queue is configured to make the hash with configured
> > information:
> > - Algorithm,
> > - key
> > - hash field (Verbs hash field)
> > - Indirection table
> > An Hash Rx queue cannot handle multiple RSS configuration, we have an Hash
> > Rx queue per protocol and thus a full configuration per protocol.
> >
> > In such situation, changing the RETA means stopping the traffic, destroying
> > every single flow, hash Rx queue, indirection table to remake everything
> > with the new configuration.
> > Until then, we always recommended to any application to restart the port on
> > this device after a RETA update to apply this new configuration.
> >
> > Since the flow API is the new way to configure flows, application should
> > move to this new one instead of using old API for such behavior.
> > We should also remove such devop from the PMD to avoid any confusion.
> >
> > Regards,
> >
> > > Thanks,
> > > Hanoh
> > >
> > > -----Original Message-----
> > > From: Yongseok Koh [mailto:ys...@mellanox.com]
> > > Sent: Wednesday, March 21, 2018 11:48 PM
> > > To: Hanoch Haim (hhaim)
> > > Cc: dev@dpdk.org
> > > Subject: Re: [dpdk-dev] mlx5 reta size is dynamic
> > >
> > > On Wed, Mar 21, 2018 at 06:56:33PM +0000, Hanoch Haim (hhaim) wrote:
> > > > Hi mlx5 driver expert,
> > > >
> > > > DPDK: 17.11
> > > > Any reason mlx5 driver change the rate table size dynamically
> > > > based on the rx- queues# ?
> > >
> > > The device only supports 2^n-sized indirection table. For example, if the
> > > number of Rx queues is 6, device can't have 1-1 mapping but the size of
> > > ind tbl could be 8, 16, 32 and so on. If we configure it as 8 for
> > > example, 2 out of 6 queues will have 1/4 of traffic while the rest 4
> > > queues receives 1/8. We thought it was too much disparity and preferred
> > > setting the max size in order to mitigate the imbalance.
> > >
> > > > There is a hidden assumption that the user wants to distribute the
> > > > packets evenly which is not always correct.
> > >
> > > But it is mostly correct because RSS is used for uniform distribution.
> > > The decision wasn't made based on our speculation but by many request
> > > from multiple customers.
> > >
> > > > /* If the requested number of RX queues is not a power of two, use the
> > > > * maximum indirection table size for better balancing.
> > > > * The result is always rounded to the next power of two. */
> > > > reta_idx_n = (1 << log2above((rxqs_n & (rxqs_n - 1)) ?
> > > > priv->ind_table_max_size :
> > > > rxqs_n));
> > >
> > > Thanks,
> > > Yongseok
> >
> > [1] https://dpdk.org/ml/archives/dev/2015-October/024668.html
> > [2] https://dpdk.org/ml/archives/dev/2015-October/024669.html
> >
> > --
> > Nélio Laranjeiro
> > 6WIND
>
> --
> Nélio Laranjeiro
> 6WIND
--
Nélio Laranjeiro
6WIND
