From: Olivier MATZ <olivier.matz@6wind.com>
To: Bruce Richardson <bruce.richardson@intel.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] mbuf: optimize first reference increment in rte_pktmbuf_attach
Date: Fri, 05 Jun 2015 11:07:57 +0200 [thread overview]
Message-ID: <557166ED.9070204@6wind.com> (raw)
In-Reply-To: <20150603105948.GC12832@bricha3-MOBL3>
Hi Bruce,
On 06/03/2015 12:59 PM, Bruce Richardson wrote:
> 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.
Good idea, I'll see if I can do that in a new version.
Thanks,
Olivier
>
> /Bruce
>
next prev parent reply other threads:[~2015-06-05 9:08 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
2015-06-05 9:07 ` Olivier MATZ [this message]
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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