[dpdk-dev] [PATCH] ixgbe: change logging for ixgbe tx code path selection

Ananyev, Konstantin konstantin.ananyev at intel.com
Tue Oct 27 13:12:39 CET 2015



> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Bruce Richardson
> Sent: Tuesday, October 27, 2015 11:50 AM
> To: Traynor, Kevin
> Cc: dev at dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] ixgbe: change logging for ixgbe tx code path selection
> 
> On Tue, Oct 27, 2015 at 11:41:08AM +0000, Kevin Traynor wrote:
> > Simple and vector are different tx code paths. If vector
> > is selected, change logging from:
> > PMD: ixgbe_set_tx_function(): Using simple tx code path
> > PMD: ixgbe_set_tx_function(): Vector tx enabled.
> >
> > to:
> > PMD: ixgbe_set_tx_function(): Using vector tx code path
> >
> > or, if simple selected:
> > PMD: ixgbe_set_tx_function(): Using simple tx code path
> >
> > The dangling else in the #ifdef makes readability difficult,
> > so resolving in way that seems most readable.
> >
> > Signed-off-by: Kevin Traynor <kevin.traynor at intel.com>
> > ---
> >  drivers/net/ixgbe/ixgbe_rxtx.c |    8 +++++---
> >  1 files changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/net/ixgbe/ixgbe_rxtx.c b/drivers/net/ixgbe/ixgbe_rxtx.c
> > index a598a72..11d7feb 100644
> > --- a/drivers/net/ixgbe/ixgbe_rxtx.c
> > +++ b/drivers/net/ixgbe/ixgbe_rxtx.c
> > @@ -1963,16 +1963,18 @@ ixgbe_set_tx_function(struct rte_eth_dev *dev, struct ixgbe_tx_queue *txq)
> >  	/* Use a simple Tx queue (no offloads, no multi segs) if possible */
> >  	if (((txq->txq_flags & IXGBE_SIMPLE_FLAGS) == IXGBE_SIMPLE_FLAGS)
> >  			&& (txq->tx_rs_thresh >= RTE_PMD_IXGBE_TX_MAX_BURST)) {
> > -		PMD_INIT_LOG(DEBUG, "Using simple tx code path");
> >  #ifdef RTE_IXGBE_INC_VECTOR
> >  		if (txq->tx_rs_thresh <= RTE_IXGBE_TX_MAX_FREE_BUF_SZ &&
> >  				(rte_eal_process_type() != RTE_PROC_PRIMARY ||
> >  					ixgbe_txq_vec_setup(txq) == 0)) {
> > -			PMD_INIT_LOG(DEBUG, "Vector tx enabled.");
> > +			PMD_INIT_LOG(DEBUG, "Using vector tx code path");
> >  			dev->tx_pkt_burst = ixgbe_xmit_pkts_vec;
> >  		} else
> >  #endif
> > -		dev->tx_pkt_burst = ixgbe_xmit_pkts_simple;
> > +		{
> > +			PMD_INIT_LOG(DEBUG, "Using simple tx code path");
> > +			dev->tx_pkt_burst = ixgbe_xmit_pkts_simple;
> > +		}
> >  	} else {
> >  		PMD_INIT_LOG(DEBUG, "Using full-featured tx code path");
> >  		PMD_INIT_LOG(DEBUG,
> > --
> > 1.7.4.1
> >
> Hi Kevin,
> 
> can I suggest a slight alternative here that might help make things easier.
> Instead of printing the message as we pick the code path, why not have a "logmsg"
> pointer variable that is assigned in the code, and then print out the log path
> at the end.
> 
> This would have a number of advantages:
> 1. there are no issues with changing our mind, so we can assign one path type,
> and then later change it to something different without cluttering up the debug
> output with the history of our code's flow.
> 2. it means that you don't have a problem with smaller else legs as you can
> easily do multiple assignments in the one line using a comma as:
> 	dev->tx_pkt_burst = ixgbe_xmit_pkts_simple, logmsg = "Using simple ...";

While I like approach with logmsg, please avoid commas here.
It will make this peace of code even more hard to read (at least for me).
Konstantin 

> 
> Regards,
> /Bruce


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