> -----Original Message-----
> From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Van Haaren, Harry
> Sent: Wednesday, September 11, 2019 12:30 PM
> To: Stephen Hemminger <step...@networkplumber.org>; Morten Brørup
> <m...@smartsharesystems.com>
> Cc: olivier.m...@6wind.com; dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] mbuf: add bulk free function
>
> > -----Original Message-----
> > From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Stephen Hemminger
> > Sent: Wednesday, September 11, 2019 12:19 PM
> > To: Morten Brørup <m...@smartsharesystems.com>
> > Cc: olivier.m...@6wind.com; dev@dpdk.org
> > Subject: Re: [dpdk-dev] [PATCH] mbuf: add bulk free function
> >
> > On Wed, 11 Sep 2019 09:19:08 +0000
> > Morten Brørup <m...@smartsharesystems.com> wrote:
> >
> > > Add function for freeing a bulk of mbufs.
> > >
> > > Signed-off-by: Morten Brørup <m...@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.
>
> I believe there's a nuance here - not all mbufs may come from the same
> mempool.
> The for() approach will free each to its "home" mempool.
> The bulk() approach may return mbufs to pools they didn't originate from.
>
> For performance reasons it would be nice if they did, but we (in the DPDK
> library)
> should not blindly assume that.
I suppose Stephen is aware of that and suggests something similar to
What many PMDs are already doing. Let say in ixgbe:
static __rte_always_inline int
ixgbe_tx_free_bufs(struct ixgbe_tx_queue *txq)
{
....
for (i = 0; i < txq->tx_rs_thresh; ++i, ++txep) {
/* free buffers one at a time */
m = rte_pktmbuf_prefree_seg(txep->mbuf);
txep->mbuf = NULL;
if (unlikely(m == NULL))
continue;
if (nb_free >= RTE_IXGBE_TX_MAX_FREE_BUF_SZ ||
(nb_free > 0 && m->pool != free[0]->pool)) {
rte_mempool_put_bulk(free[0]->pool,
(void **)free, nb_free);
nb_free = 0;
}
free[nb_free++] = m;
}
}
Of course generic function will also need to go through all segments in each
packet.
> We could consider adding a 2nd functions,
> rte_pktmbuf_free_bulk_to_single_mempool()
> or some better descriptive name.
Probably a good idea too.
Konstantin
