Re: [dpdk-dev] [PATCH v2 01/15] net/mlx5: support 16 hardware priorities

["Xueming(Steven) Li" <xuemingl@mellanox.com>]

> -----Original Message-----
> From: Nélio Laranjeiro <nelio.laranjeiro@6wind.com>
> Sent: Thursday, April 12, 2018 10:03 PM
> To: Xueming(Steven) Li <xuemingl@mellanox.com>
> Cc: Shahaf Shuler <shahafs@mellanox.com>; dev@dpdk.org
> Subject: Re: [PATCH v2 01/15] net/mlx5: support 16 hardware priorities
> 
> On Thu, Apr 12, 2018 at 01:43:04PM +0000, Xueming(Steven) Li wrote:
> >
> >
> > > -----Original Message-----
> > > From: Nélio Laranjeiro <nelio.laranjeiro@6wind.com>
> > > Sent: Thursday, April 12, 2018 5:09 PM
> > > To: Xueming(Steven) Li <xuemingl@mellanox.com>
> > > Cc: Shahaf Shuler <shahafs@mellanox.com>; dev@dpdk.org
> > > Subject: Re: [PATCH v2 01/15] net/mlx5: support 16 hardware
> > > priorities
> > >
> > > On Tue, Apr 10, 2018 at 03:22:46PM +0000, Xueming(Steven) Li wrote:
> > > > Hi Nelio,
> > > >
> > > > > -----Original Message-----
> > > > > From: Nélio Laranjeiro <nelio.laranjeiro@6wind.com>
> > > > > Sent: Tuesday, April 10, 2018 10:42 PM
> > > > > To: Xueming(Steven) Li <xuemingl@mellanox.com>
> > > > > Cc: Shahaf Shuler <shahafs@mellanox.com>; dev@dpdk.org
> > > > > Subject: Re: [PATCH v2 01/15] net/mlx5: support 16 hardware
> > > > > priorities
> > > > >
> > > > > On Tue, Apr 10, 2018 at 09:34:01PM +0800, Xueming Li wrote:
> > > > > > Adjust flow priority mapping to adapt new hardware 16 verb
> > > > > > flow priorites support:
> > > > > > 0-3: RTE FLOW tunnel rule
> > > > > > 4-7: RTE FLOW non-tunnel rule
> > > > > > 8-15: PMD control flow
> > > > >
> > > > > This commit log is inducing people in error, this amount of
> > > > > priority depends on the Mellanox OFED installed, it is not
> > > > > available on upstream Linux kernel yet nor in the current Mellanox
> OFED GA.
> > > > >
> > > > > What happens when those amount of priority are not available, is
> > > > > it removing a functionality?  Will it collide with other flows?
> > > >
> > > > If 16  priorities not available, simply behavior as 8 priorities.
> > >
> > > It is not described in the commit log, please add it.
> > >
> > > > > > Signed-off-by: Xueming Li <xuemingl@mellanox.com>
> > > <snip/>
> > > > > >  	},
> > > > > >  	[HASH_RXQ_ETH] = {
> > > > > >  		.hash_fields = 0,
> > > > > >  		.dpdk_rss_hf = 0,
> > > > > > -		.flow_priority = 3,
> > > > > > +		.flow_priority = 2,
> > > > > >  	},
> > > > > >  };
> > > > >
> > > > > If the amount of priorities remains 8, you are removing the
> > > > > priority for the tunnel flows introduced by commit 749365717f5c
> ("net/mlx5:
> > > > > change tunnel flow priority")
> > > > >
> > > > > Please keep this functionality when this patch fails to get the
> > > > > expected
> > > > > 16 Verbs priorities.
> > > >
> > > > These priority shift are different in 16 priorities scenario, I
> > > > changed it to calculation. In function
> > > > mlx5_flow_priorities_detect(), priority shift will be 1 if 8
> priorities, 4 in case of 16 priorities.
> > > > Please refer to changes in function mlx5_flow_update_priority() as
> well.
> > >
> > > Please light my lamp, I don't see it...
> >
> > Sorry, please refer to priv->config.flow_priority_shift.
> >
> > >
> > > <snip/>
> > > > > >  static void
> > > > > > -mlx5_flow_update_priority(struct mlx5_flow_parse *parser,
> > > > > > +mlx5_flow_update_priority(struct rte_eth_dev *dev,
> > > > > > +			  struct mlx5_flow_parse *parser,
> > > > > >  			  const struct rte_flow_attr *attr)  {
> > > > > > +	struct priv *priv = dev->data->dev_private;
> > > > > >  	unsigned int i;
> > > > > > +	uint16_t priority;
> > > > > >
> > > > > > +	if (priv->config.flow_priority_shift == 1)
> > > > > > +		priority = attr->priority * MLX5_VERBS_FLOW_PRIO_4;
> > > > > > +	else
> > > > > > +		priority = attr->priority * MLX5_VERBS_FLOW_PRIO_8;
> > > > > > +	if (!parser->inner)
> > > > > > +		priority += priv->config.flow_priority_shift;
> >
> > Here, if non-tunnel flow, lower(increase) 1 for 8 priorities, lower 4
> otherwise.
> > I'll append a comment here.
> 
> Thanks, I totally missed this one.
> 
> <snip/>
> > > > > > diff --git a/drivers/net/mlx5/mlx5_trigger.c
> > > > > > b/drivers/net/mlx5/mlx5_trigger.c index 6bb4ffb14..d80a2e688
> > > > > > 100644
> > > > > > --- a/drivers/net/mlx5/mlx5_trigger.c
> > > > > > +++ b/drivers/net/mlx5/mlx5_trigger.c
> > > > > > @@ -148,12 +148,6 @@ mlx5_dev_start(struct rte_eth_dev *dev)
> > > > > >  	int ret;
> > > > > >
> > > > > >  	dev->data->dev_started = 1;
> > > > > > -	ret = mlx5_flow_create_drop_queue(dev);
> > > > > > -	if (ret) {
> > > > > > -		DRV_LOG(ERR, "port %u drop queue allocation failed: %s",
> > > > > > -			dev->data->port_id, strerror(rte_errno));
> > > > > > -		goto error;
> > > > > > -	}
> > > > > >  	DRV_LOG(DEBUG, "port %u allocating and configuring hash Rx
> > > queues",
> > > > > >  		dev->data->port_id);
> > > > > >  	rte_mempool_walk(mlx5_mp2mr_iter, priv); @@ -202,7 +196,6 @@
> > > > > > mlx5_dev_start(struct rte_eth_dev *dev)
> > > > > >  	mlx5_traffic_disable(dev);
> > > > > >  	mlx5_txq_stop(dev);
> > > > > >  	mlx5_rxq_stop(dev);
> > > > > > -	mlx5_flow_delete_drop_queue(dev);
> > > > > >  	rte_errno = ret; /* Restore rte_errno. */
> > > > > >  	return -rte_errno;
> > > > > >  }
> > > > > > @@ -237,7 +230,6 @@ mlx5_dev_stop(struct rte_eth_dev *dev)
> > > > > >  	mlx5_rxq_stop(dev);
> > > > > >  	for (mr = LIST_FIRST(&priv->mr); mr; mr = LIST_FIRST(&priv-
> > > >mr))
> > > > > >  		mlx5_mr_release(mr);
> > > > > > -	mlx5_flow_delete_drop_queue(dev);
> > > > > >  }
> > > > > >
> > > > > >  /**
> > > > > > --
> > > > > > 2.13.3
> > > > >
> > > > > I have few concerns on this, mlx5_pci_probe() will also probe
> > > > > any under layer verbs device, and in a near future the
> > > > > representors associated to a VF.
> > > > > Making such detection should only be done once by the PF, I also
> > > > > wander if it is possible to make such drop action in a
> > > > > representor directly using Verbs.
> > > >
> > > > Then there should be some work to disable flows in representors?
> > > > that supposed to cover this.
> > >
> > > The code raising another Verbs device is already present and since
> > > the first entrance of this PMD in the DPDK tree, you must respect
> > > the code already present.
> > > This request is not related directly to a new feature but to an
> > > existing one, the representors being just an example.
> > >
> > > This detection should be only done once and not for each of them.
> >
> > Could you please elaborate on "under layer verbs device" and how to
> > judge dependency to PF, is there a probe order between them?
> 
> The place where you are adding the mlx5_flow_create_drop_queue() in
> mlx5_pci_probe() is probing any device returned by the verbs
> ibv_get_device_list().
> 
> This code is also present in mlx4 where for a single PCI id there are 2
> physical ports.
> 
> If the NIC handle several ibvdev (Verbs devices) it will create a new
> rte_eth_dev for each one.
> 
> > BTW, VF representor code seems exists in 17.11, not upstream.
> >
> > >
> > > > > Another concern is, this patch will be reverted in some time
> > > > > when those
> > > > > 16 priority will be always available.  It will be easier to
> > > > > remove this detection function than searching for all those
> modifications.
> > > > >
> > > > > I would suggest to have a standalone
> > > > > mlx5_flow_priorities_detect() which creates and deletes all
> resources needed for this detection.
> > > >
> > > > There is an upcoming new feature to support priorities more than
> > > > 16, auto detection will be kept IMHO.
> > >
> > > Until the final values of priorities will be backported to all
> > > kernels we support.  You don't see far enough in the future.
> > >
> > > > Besides, there will be a bundle of resource creation and removal
> > > > in this standalone function, I'm not sure it valuable to duplicate
> > > > them, please refer to function mlx5_flow_create_drop_queue().
> > >
> > > You misunderstood, I am not asking you to not use the default drop
> > > queues but instead of making an rte_flow attributes, items and
> > > actions to make directly the Verbs specification on the stack.  It
> > > will be faster than making a bunch of conversions (relying on
> > > malloc) from rte_flow to Verbs whereas you know exactly what it needs
> i.e. 1 spec.
> >
> > Sorry, still confused, mlx5_flow_priorities_detect() invokes
> > ibv_destroy_flow(), not rte_flow stuff, no malloc at all. BTW, mlx5
> > flow api bypass verb flow in offline mode, we can't use it to create
> flows at such stage.
> 
> Sorry I was the one confused. Priority detection is Ok.
> 
> After reading this, I'll suggest to use a boolean in the
> mlx5_pci_probe() to only make this detection once, the underlying verbs
> devices will inherit from such knowledge and adjust their own shift
> accordingly.
> 
> What do you think?

Finally got it, fortunately, Shahaf has similar suggestion in 17.11 review.
I'll make mlx5_flow_priorities_detect() simply return number of supported 
priorities, and this number will be used to make this function rule only once
in loop. Many thanks for your suggestion, I'm interpreting it in complex.

BTW, if no other comments on this series, I'll upload a new version.

> 
> --
> Nélio Laranjeiro
> 6WIND