From: Bruce Richardson <bruce.richardson@intel.com>
To: Olivier Matz <olivier.matz@6wind.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] mbuf: optimize first reference increment in rte_pktmbuf_attach
Date: Wed, 3 Jun 2015 11:59:49 +0100 [thread overview]
Message-ID: <20150603105948.GC12832@bricha3-MOBL3> (raw)
In-Reply-To: <1433151145-8176-1-git-send-email-olivier.matz@6wind.com>
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@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
next prev parent reply other threads:[~2015-06-03 10:59 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-01 9:32 Olivier Matz
2015-06-03 10:59 ` Bruce Richardson [this message]
2015-06-05 9:07 ` Olivier MATZ
2015-06-08 14:57 ` [dpdk-dev] [PATCH v2] mbuf: optimize rte_mbuf_refcnt_update Olivier Matz
2015-06-09 12:57 ` Bruce Richardson
2015-06-12 14:10 ` Thomas Monjalon
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