On Mon, Jun 01, 2015 at 11:32:25AM +0200, Olivier Matz wrote: > As it's done in __rte_pktmbuf_prefree_seg(), we can avoid using an > atomic increment in rte_pktmbuf_attach() by checking if we are the > only owner of the mbuf first. > > Signed-off-by: Olivier Matz <olivier.matz at 6wind.com> > --- > lib/librte_mbuf/rte_mbuf.h | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h > index ab6de67..cea35b7 100644 > --- a/lib/librte_mbuf/rte_mbuf.h > +++ b/lib/librte_mbuf/rte_mbuf.h > @@ -838,7 +838,11 @@ static inline void rte_pktmbuf_attach(struct rte_mbuf > *mi, struct rte_mbuf *m) > else > md = rte_mbuf_from_indirect(m); > > - rte_mbuf_refcnt_update(md, 1); > + /* optimize the case where we are the only owner */ > + if (likely(rte_mbuf_refcnt_read(md) == 1)) > + rte_mbuf_refcnt_set(md, 2); > + else > + rte_mbuf_refcnt_update(md, 1); > mi->priv_size = m->priv_size; > mi->buf_physaddr = m->buf_physaddr; > mi->buf_addr = m->buf_addr; > -- > 2.1.4 > Why not make the change inside rte_mbuf_refcnt_update itself? If it is ever called with a current refcnt of 1, it should always be safe to do the update without a cmpset.
/Bruce
