From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: "Chen, Junjie J" <junjie.j.chen@intel.com>,
"Xing, Beilei" <beilei.xing@intel.com>,
"Zhang, Qi Z" <qi.z.zhang@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
"Chen, Junjie J" <junjie.j.chen@intel.com>,
"Chen@dpdk.org" <Chen@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] net/i40e: update tx_free_threshold to improve zero copy performance
Date: Thu, 12 Apr 2018 11:51:36 +0000 [thread overview]
Message-ID: <2601191342CEEE43887BDE71AB977258AE9143FC@IRSMSX102.ger.corp.intel.com> (raw)
In-Reply-To: <20180412053226.295226-1-junjie.j.chen@intel.com>
> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Junjie Chen
> Sent: Thursday, April 12, 2018 6:32 AM
> To: Xing, Beilei <beilei.xing@intel.com>; Zhang, Qi Z <qi.z.zhang@intel.com>
> Cc: dev@dpdk.org; Chen, Junjie J <junjie.j.chen@intel.com>; Chen@dpdk.org
> Subject: [dpdk-dev] [PATCH] net/i40e: update tx_free_threshold to improve zero copy performance
>
> From: "Chen, Junjie" <junjie.j.chen@intel.com>
>
> When vhost backend works in dequeue zero copy mode, nic locks virtio's
> buffer until there is less or equal than tx_free_threshold buffer remain
> and then free number of tx burst buffer. This causes packets drop in
> virtio side and impacts zero copy performance. So we need to increase
> the tx_free_threshold to let nic free virtio's buffer as soon as possible.
> Also we keep the upper limit to tx max burst size to ensure least
> performance impact on non zero copy.
Ok but why vhost app can't just use tx_queue_setup() to specify desired value for
tx_free_thresh?
Why instead we have to modify PMD to satisfy needs of one app?
Konstantin
>
> Signed-off-by: Chen, Junjie <junjie.j.chen@intel.com>
> ---
> drivers/net/i40e/i40e_rxtx.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/net/i40e/i40e_rxtx.c b/drivers/net/i40e/i40e_rxtx.c
> index 56a854cec..d9569bdc9 100644
> --- a/drivers/net/i40e/i40e_rxtx.c
> +++ b/drivers/net/i40e/i40e_rxtx.c
> @@ -2039,6 +2039,8 @@ i40e_dev_tx_queue_setup(struct rte_eth_dev *dev,
> tx_conf->tx_rs_thresh : DEFAULT_TX_RS_THRESH);
> tx_free_thresh = (uint16_t)((tx_conf->tx_free_thresh) ?
> tx_conf->tx_free_thresh : DEFAULT_TX_FREE_THRESH);
> + if (tx_free_thresh < nb_desc - I40E_TX_MAX_BURST)
> + tx_free_thresh = nb_desc - I40E_TX_MAX_BURST;
> if (tx_rs_thresh >= (nb_desc - 2)) {
> PMD_INIT_LOG(ERR, "tx_rs_thresh must be less than the "
> "number of TX descriptors minus 2. "
> --
> 2.16.0
next prev parent reply other threads:[~2018-04-12 11:51 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-12 5:32 Junjie Chen
2018-04-12 11:51 ` Ananyev, Konstantin [this message]
2018-04-12 12:20 ` Zhang, Qi Z
2018-04-12 13:12 ` Bruce Richardson
2018-04-12 13:56 ` Ananyev, Konstantin
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