Hi Matan, On Mon, Oct 30, 2017 at 06:11:31PM +0000, Matan Azrad wrote: > Hi Adrien > > > -----Original Message----- > > From: Adrien Mazarguil [mailto:adrien.mazarg...@6wind.com] > > Sent: Monday, October 30, 2017 4:23 PM > > To: Matan Azrad <ma...@mellanox.com> > > Cc: dev@dpdk.org; Ophir Munk <ophi...@mellanox.com> > > Subject: Re: [PATCH v3 1/7] net/mlx4: remove error flows from Tx fast path > > > > On Mon, Oct 30, 2017 at 10:07:23AM +0000, Matan Azrad wrote: > > > Move unnecessary error flows to DEBUG mode. > > > > > > Signed-off-by: Matan Azrad <ma...@mellanox.com> > > > Acked-by: Adrien Mazarguil <adrien.mazarg...@6wind.com> > > > > I missed a couple of details while reviewing the original version, the > > first one > > being mlx4_post_send()'s return value is still documented as updating > > rte_errno in case of error, it's not the case anymore after this patch. > > > Good attention, Will be fixed in next version. > > > Please see below for the other one: > > > > > --- > > > drivers/net/mlx4/mlx4_rxtx.c | 16 ++++++---------- > > > 1 file changed, 6 insertions(+), 10 deletions(-) > > > > > > diff --git a/drivers/net/mlx4/mlx4_rxtx.c > > > b/drivers/net/mlx4/mlx4_rxtx.c > > <snip> > > > /** > > > @@ -510,8 +508,6 @@ struct pv { > > > assert(max <= elts_n); > > > /* Always leave one free entry in the ring. */ > > > --max; > > > - if (max == 0) > > > - return 0; > > > if (max > pkts_n) > > > max = pkts_n; > > > for (i = 0; (i != max); ++i) { > > > > While minor, this change has nothing to do with this patch, right? > > > Yes you right, maybe it can be merged in patch 4/7. > > > I think it can slightly degrade an application performance as it removes the > > guarantee that subsequent code only needs to be run if there is at least one > > packet to process in case the TX ring is constantly full (SW faster than > > HW). > > > > In case the TX ring is full, the loop condition should fail in the start and > then return with 0 because the packet counter is 0.(more 2 checks) > Since this case are less common (in my opinion) than at least 1 free space in > ring, we can prevent this unnecessary check for all these common cases. > > Are you sure the 2 extra check important for performance in this empty case? > Doesn't the application will call us again?
No, I don't think they're important to performance, like the changes from patch 4/7, I'm not certain they actually make any difference. My suggestion was mainly to leave it alone because of that. It's OK if you want to keep and move it to 4/7. -- Adrien Mazarguil 6WIND
