From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: Jerin Jacob <jerin.jacob@caviumnetworks.com>,
"dev@dpdk.org" <dev@dpdk.org>
Cc: "thomas.monjalon@6wind.com" <thomas.monjalon@6wind.com>
Subject: Re: [dpdk-dev] [PATCH] ring: fix sc dequeue performance issue
Date: Sun, 24 Jul 2016 22:57:38 +0000 [thread overview]
Message-ID: <2601191342CEEE43887BDE71AB97725836B817D7@irsmsx105.ger.corp.intel.com> (raw)
In-Reply-To: <1469380060-26696-1-git-send-email-jerin.jacob@caviumnetworks.com>
> -----Original Message-----
> From: Jerin Jacob [mailto:jerin.jacob@caviumnetworks.com]
> Sent: Sunday, July 24, 2016 6:08 PM
> To: dev@dpdk.org
> Cc: thomas.monjalon@6wind.com; Ananyev, Konstantin <konstantin.ananyev@intel.com>; Jerin Jacob
> <jerin.jacob@caviumnetworks.com>
> Subject: [dpdk-dev] [PATCH] ring: fix sc dequeue performance issue
>
> Use of rte_smb_wmb() instead of rte_smb_rmb() in sc dequeue function creates the additional overhead of waiting for all the STOREs to be
> completed to local buffer from ring buffer memory. The sc dequeue function demands only LOAD-STORE barrier where LOADs from ring
> buffer memory needs to be completed before tail pointer update. Changing to rte_smb_rmb() to enable the required LOAD-STORE barrier.
>
> Fixes: ecc7d10e448e ("ring: guarantee dequeue ordering before tail update")
>
> Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> ---
> lib/librte_ring/rte_ring.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h index f928324..0e22e69 100644
> --- a/lib/librte_ring/rte_ring.h
> +++ b/lib/librte_ring/rte_ring.h
> @@ -756,7 +756,7 @@ __rte_ring_sc_do_dequeue(struct rte_ring *r, void **obj_table,
>
> /* copy in table */
> DEQUEUE_PTRS();
> - rte_smp_wmb();
> + rte_smp_rmb();
>
> __RING_STAT_ADD(r, deq_success, n);
> r->cons.tail = cons_next;
> --
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
> 2.5.5
next prev parent reply other threads:[~2016-07-24 22:57 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-24 17:07 Jerin Jacob
2016-07-24 22:57 ` Ananyev, Konstantin [this message]
2016-07-25 14:54 ` Thomas Monjalon
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