Re: [Intel-wired-lan] [PATCH V2 net] ice: Re-organizes reqstd/avail {R, T}XQ check/code for efficiency+readability

[Paul Menzel]

[CC: Remove Jeff, as email is rejected]

Dear Salil,


Am 21.04.21 um 09:41 schrieb Salil Mehta:
> > From: Paul Menzel [mailto:pmenzel@xxxxxxxxxxxxx]
> > Sent: Wednesday, April 21, 2021 6:36 AM

[…]

> > In the git commit message summary, could you please use imperative mood [1]?
>
> No issues. There is always a scope of improvement.
>
> > > Re-organize reqstd/avail {R, T}XQ check/code for efficiency+readability
> >
> > It’s a bit long though. Maybe:
> >
> > Avoid unnecessary assignment with user specified {R,T}XQs
>
> Umm..above conveys the wrong meaning as this is not what patch is doing.
>
> If you see the code, in the presence of the user specified {R,T}XQs it
> avoids fetching available {R,T}XQ count.
>
> What about below?
>
> "Avoid unnecessary avail_{r,t}xq assignments if user has specified Qs"

Sounds good, still a little long. Maybe:

> Avoid unnecessary avail_{r,t}xq assignments with user specified Qs

> > Am 14.04.21 um 00:44 schrieb Salil Mehta:
> > > If user has explicitly requested the number of {R,T}XQs, then it is
> > > unnecessary to get the count of already available {R,T}XQs from the
> > > PF avail_{r,t}xqs bitmap. This value will get overridden by user specified
> > > value in any case.
> > >
> > > This patch does minor re-organization of the code for improving the flow
> > > and readabiltiy. This scope of improvement was found during the review of
> >
> > readabil*it*y
>
> Thanks. Missed that earlier. My shaky fingers :(
>
> > > the ICE driver code.
> > >
> > > FYI, I could not test this change due to unavailability of the hardware.
> > > It would be helpful if somebody can test this patch and provide Tested-by
> > > Tag. Many thanks!
> >
> > This should go outside the commit message (below the --- for example).
>
> Agreed.
>
> > > Fixes: 87324e747fde ("ice: Implement ethtool ops for channels")
> >
> > Did you check the behavior before is actually a bug? Or is it just for
> > the detection heuristic for commits to be applied to the stable series?
>
> Right, later was the idea.
>   
> > > Cc: intel-wired-lan@xxxxxxxxxxxxxxxx
> > > Cc: Jeff Kirsher <jeffrey.t.kirsher@xxxxxxxxx>
> > > Signed-off-by: Salil Mehta <salil.mehta@xxxxxxxxxx>
> > > --
> > > Change V1->V2
> > >    (*) Fixed the comments from Anthony Nguyen(Intel)
> > >        Link: https://lkml.org/lkml/2021/4/12/1997
> > > ---
> > >    drivers/net/ethernet/intel/ice/ice_lib.c | 14 ++++++++------
> > >    1 file changed, 8 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/intel/ice/ice_lib.c b/drivers/net/ethernet/intel/ice/ice_lib.c
> > > index d13c7fc8fb0a..d77133d6baa7 100644
> > > --- a/drivers/net/ethernet/intel/ice/ice_lib.c
> > > +++ b/drivers/net/ethernet/intel/ice/ice_lib.c
> > > @@ -161,12 +161,13 @@ static void ice_vsi_set_num_qs(struct ice_vsi *vsi, u16 vf_id)
> > >
> > >    	switch (vsi->type) {
> > >    	case ICE_VSI_PF:
> > > -		vsi->alloc_txq = min3(pf->num_lan_msix,
> > > -				      ice_get_avail_txq_count(pf),
> > > -				      (u16)num_online_cpus());
> > >    		if (vsi->req_txq) {
> > >    			vsi->alloc_txq = vsi->req_txq;
> > >    			vsi->num_txq = vsi->req_txq;
> > > +		} else {
> > > +			vsi->alloc_txq = min3(pf->num_lan_msix,
> > > +					      ice_get_avail_txq_count(pf),
> > > +					      (u16)num_online_cpus());
> > >    		}
> >
> > I am curious, did you check the compiler actually creates different
> > code, or did it notice the inefficiency by itself and optimized it already?
>
> I have not looked into that detail but irrespective of what compiler generates
> I would like to keep the code in a shape which is more efficient and more readable.
>
> I do understand in certain cases we have to do tradeoff between efficiency
> and readability but I do not see that here.

I agree, as *efficiency* is mentioned several times, I assume it was 
tested. Thank you for the clarification.

> > >    		pf->num_lan_tx = vsi->alloc_txq;
> > > @@ -175,12 +176,13 @@ static void ice_vsi_set_num_qs(struct ice_vsi *vsi, u16 vf_id)
> > >    		if (!test_bit(ICE_FLAG_RSS_ENA, pf->flags)) {
> > >    			vsi->alloc_rxq = 1;
> > >    		} else {
> > > -			vsi->alloc_rxq = min3(pf->num_lan_msix,
> > > -					      ice_get_avail_rxq_count(pf),
> > > -					      (u16)num_online_cpus());
> > >    			if (vsi->req_rxq) {
> > >    				vsi->alloc_rxq = vsi->req_rxq;
> > >    				vsi->num_rxq = vsi->req_rxq;
> > > +			} else {
> > > +				vsi->alloc_rxq = min3(pf->num_lan_msix,
> > > +						      ice_get_avail_rxq_count(pf),
> > > +						      (u16)num_online_cpus());
> > >    			}
> > >    		}


Kind regards,

Paul