From: "Zhang, Qi Z" <qi.z.zhang@intel.com>
To: Joyce Kong <joyce.kong@arm.com>,
"Xing, Beilei" <beilei.xing@intel.com>,
"ruifeng.wang@arm.com" <ruifeng.wang@arm.com>,
"honnappa.nagarahalli@arm.com" <honnappa.nagarahalli@arm.com>,
"Richardson, Bruce" <bruce.richardson@intel.com>,
"Zhang, Helin" <helin.zhang@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
"stable@dpdk.org" <stable@dpdk.org>, "nd@arm.com" <nd@arm.com>
Subject: Re: [dpdk-dev] [PATCH v3 2/2] net/i40e: replace SMP barrier with thread fence
Date: Thu, 8 Jul 2021 12:09:08 +0000 [thread overview]
Message-ID: <061d231c5ff848a19be50a62aed44087@intel.com> (raw)
In-Reply-To: <20210706065404.25137-3-joyce.kong@arm.com>
> -----Original Message-----
> From: Joyce Kong <joyce.kong@arm.com>
> Sent: Tuesday, July 6, 2021 2:54 PM
> To: Xing, Beilei <beilei.xing@intel.com>; Zhang, Qi Z <qi.z.zhang@intel.com>;
> ruifeng.wang@arm.com; honnappa.nagarahalli@arm.com; Richardson, Bruce
> <bruce.richardson@intel.com>; Zhang, Helin <helin.zhang@intel.com>
> Cc: dev@dpdk.org; stable@dpdk.org; nd@arm.com
> Subject: [PATCH v3 2/2] net/i40e: replace SMP barrier with thread fence
>
> Simply replace the SMP barrier with atomic thread fence for i40e hw ring sacn,
> if there is no synchronization point.
>
> Signed-off-by: Joyce Kong <joyce.kong@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> ---
> drivers/net/i40e/i40e_rxtx.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/i40e/i40e_rxtx.c b/drivers/net/i40e/i40e_rxtx.c index
> 9aaabfd92..86e2f083e 100644
> --- a/drivers/net/i40e/i40e_rxtx.c
> +++ b/drivers/net/i40e/i40e_rxtx.c
> @@ -482,7 +482,8 @@ i40e_rx_scan_hw_ring(struct i40e_rx_queue *rxq)
> I40E_RXD_QW1_STATUS_SHIFT;
> }
>
> - rte_smp_rmb();
> + /* This barrier is to order loads of different words in the descriptor */
> + rte_atomic_thread_fence(__ATOMIC_ACQUIRE);
Now for x86, you actually replace a compiler barrier with a memory fence, this may have potential performance impact which need additional resource to investigate
So there are 2 options:
1. if you want this patch be merged into DPDK 21.08, please change this for ARM only.
2. you can wait for our update for x86 but I guess it will miss 21.08.
What do you think?
Btw for patch 1/2, I think I can merge it independently right?
>
> /* Compute how many status bits were set */
> for (j = 0, nb_dd = 0; j < I40E_LOOK_AHEAD; j++) {
> --
> 2.17.1
next prev parent reply other threads:[~2021-07-08 12:09 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-04 7:34 [dpdk-dev] [PATCH v1] net/i40e: remove the SMP barrier in HW scanning func Joyce Kong
2021-06-04 16:12 ` Honnappa Nagarahalli
2021-06-06 14:17 ` Zhang, Qi Z
2021-06-06 18:33 ` Honnappa Nagarahalli
2021-06-07 14:55 ` Zhang, Qi Z
2021-06-07 21:36 ` Honnappa Nagarahalli
2021-06-15 6:30 ` Joyce Kong
2021-06-16 13:29 ` Zhang, Qi Z
2021-06-16 13:37 ` Bruce Richardson
2021-06-16 20:26 ` Honnappa Nagarahalli
2021-06-23 8:43 ` [dpdk-dev] [PATCH v2] net/i40e: add logic of processing continuous DD bits for Arm Joyce Kong
2021-06-30 1:14 ` Honnappa Nagarahalli
2021-07-05 3:41 ` Joyce Kong
2021-07-06 6:54 ` [dpdk-dev] [PATCH v3 0/2] fixes for i40e hw scan ring Joyce Kong
2021-07-06 6:54 ` [dpdk-dev] [PATCH v3 1/2] net/i40e: add logic of processing continuous DD bits for Arm Joyce Kong
2021-07-09 3:05 ` Zhang, Qi Z
2021-07-06 6:54 ` [dpdk-dev] [PATCH v3 2/2] net/i40e: replace SMP barrier with thread fence Joyce Kong
2021-07-08 12:09 ` Zhang, Qi Z [this message]
2021-07-08 13:51 ` Lance Richardson
2021-07-08 14:26 ` Zhang, Qi Z
2021-07-08 14:44 ` Honnappa Nagarahalli
2021-07-13 0:46 ` Zhang, Qi Z
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