Re: [dpdk-dev] [PATCH v7 1/2] ring: add reset API to flush the ring when not in use

[Olivier Matz <olivier.matz@6wind.com>]

Hi Gavin,

On Fri, Jul 12, 2019 at 11:06:28AM +0000, Gavin Hu (Arm Technology China) wrote:
> Hi Olivier,
> 
> > -----Original Message-----
> > From: Olivier Matz <olivier.matz@6wind.com>
> > Sent: Friday, July 12, 2019 5:54 PM
> > To: Gavin Hu (Arm Technology China) <Gavin.Hu@arm.com>
> > Cc: thomas@monjalon.net; dev@dpdk.org; nd <nd@arm.com>;
> > jerinj@marvell.com; hemant.agrawal@nxp.com; Nipun.gupta@nxp.com;
> > Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>;
> > i.maximets@samsung.com; stable@dpdk.org
> > Subject: Re: [dpdk-dev] [PATCH v7 1/2] ring: add reset API to flush the ring
> > when not in use
> > 
> > Hi Gavin,
> > 
> > On Fri, Jul 12, 2019 at 09:32:39AM +0000, Gavin Hu (Arm Technology China)
> > wrote:
> > > Hi Olivier and Thomas,
> > >
> > > > -----Original Message-----
> > > > From: Thomas Monjalon <thomas@monjalon.net>
> > > > Sent: Thursday, July 4, 2019 10:42 PM
> > > > To: Gavin Hu (Arm Technology China) <Gavin.Hu@arm.com>
> > > > Cc: dev@dpdk.org; Olivier Matz <olivier.matz@6wind.com>; nd
> > > > <nd@arm.com>; jerinj@marvell.com; hemant.agrawal@nxp.com;
> > > > Nipun.gupta@nxp.com; Honnappa Nagarahalli
> > > > <Honnappa.Nagarahalli@arm.com>; i.maximets@samsung.com;
> > > > stable@dpdk.org
> > > > Subject: Re: [dpdk-dev] [PATCH v7 1/2] ring: add reset API to flush the ring
> > > > when not in use
> > > >
> > > > 29/03/2019 15:17, Olivier Matz:
> > > > > Hi,
> > > > >
> > > > > On Fri, Mar 15, 2019 at 11:31:25AM +0800, Gavin Hu wrote:
> > > > > > Currently, the flush is done by dequeuing the ring in a while loop. It is
> > > > > > much simpler to flush the queue by resetting the head and tail indices.
> > > > > >
> > > > > > Fixes: af75078fece3 ("first public release")
> > > > > > Cc: stable@dpdk.org
> > > > > >
> > > > > > Signed-off-by: Gavin Hu <gavin.hu@arm.com>
> > > > > > Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> > > > > > Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> > > > > > ---
> > > > > > --- a/lib/librte_ring/rte_ring_version.map
> > > > > > +++ b/lib/librte_ring/rte_ring_version.map
> > > > > > @@ -17,3 +17,10 @@ DPDK_2.2 {
> > > > > >  	rte_ring_free;
> > > > > >
> > > > > >  } DPDK_2.0;
> > > > > > +
> > > > > > +EXPERIMENTAL {
> > > > > > +    global:
> > > > > > +
> > > > > > +	rte_ring_reset;
> > > > > > +
> > > > > > +};
> > > > >
> > > > > To me, a static inline function does not need to be added in
> > > > > rte_ring_version.map (or is it due to a check script checking the
> > > > > __rte_experimental tag ?). I found at least one commit where it
> > > > > is not the case:
> > > > > c277b34c1b3b ("mbuf: add function returning buffer address")
> > > > >
> > > > > There are 2 options:
> > > > > 1- remove the rte_ring_version.map part of the patch.
> > > > > 2- change the static inline function into a standard function.
> > > > >
> > > > > I would prefer 2-, because it allows to keep an api/abi compat
> > > > > layer in the future.
> > > >
> > > > There are no news about this patch.
> > > > I classify it as changes requested.
> > > >
> > > Sorry for missed your comments for long time, I just submitted v8.
> > > I took the first option as it is in the data path and to keep consistent to its
> > neighboring functions.
> > 
> > Could you give a little more context about why you need to reset
> > the ring in the data path? I see that it is used in rte_hash_reset(),
> > but in my thinking, this was more used at init/exit.
> Sorry，literally it is in the control path, but I was impressed it will impact the 
> Data path performance when discussing this patch with Honnappa. 

I'm asking this because given the recent discussions about ABI stability,
I'd like to avoid defining a new static inline if it is not required.

Thanks,
Olivier