Re: [dpdk-dev] [PATCH] mbuf: add bulk free function

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 11 Sep 2019 13:33:13 +0200
Olivier Matz <olivier.matz@6wind.com> wrote:

> Hi,
> 
> On Wed, Sep 11, 2019 at 12:18:34PM +0100, Stephen Hemminger wrote:
> > On Wed, 11 Sep 2019 09:19:08 +0000
> > Morten Brørup <mb@smartsharesystems.com> wrote:
> >   
> > > Add function for freeing a bulk of mbufs.
> > > 
> > > Signed-off-by: Morten Brørup <mb@smartsharesystems.com>
> > > ---
> > >  lib/librte_mbuf/rte_mbuf.h | 17 +++++++++++++++++
> > >  1 file changed, 17 insertions(+)
> > > 
> > > diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> > > index 98225ec80..f2e174da1 100644
> > > --- a/lib/librte_mbuf/rte_mbuf.h
> > > +++ b/lib/librte_mbuf/rte_mbuf.h
> > > @@ -1907,6 +1907,23 @@ static inline void rte_pktmbuf_free(struct rte_mbuf *m)
> > >  	}
> > >  }
> > >  
> > > +/**
> > > + * Free a bulk of mbufs back into their original mempool.
> > > + *
> > > + *  @param mbufs
> > > + *    Array of pointers to mbufs
> > > + *  @param count
> > > + *    Array size
> > > + */
> > > +static inline void
> > > +rte_pktmbuf_free_bulk(struct rte_mbuf **mbufs, unsigned count)
> > > +{
> > > +	unsigned idx = 0;
> > > +
> > > +	for (idx = 0; idx < count; idx++)
> > > +		rte_pktmbuf_free(mbufs[idx]);
> > > +}
> > > +  
> > 
> > You can optimize this to use mempool bulk put operation.  
> 
> A bulk free for mbuf is not as simple as a bulk mempool put, because
> of indirect mbufs, and because mbufs may return in different mempools.
> 
> Morten, do you have more details about why do you need such a function?
> 
> Thanks,
> Olivier

I was thinking of a function that looked at the list and if they were all
the same pool and safe to bulk put, then use that as a fast path. This would
be the most common case.

Also, less inline functions please. When it is an inline it adds more API/ABI
dependencies.