From: Jakub Kicinski <kuba@kernel.org>
To: <yang.yang29@zte.com.cn>
Cc: <edumazet@google.com>, <davem@davemloft.net>,
<netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<xu.xin16@zte.com.cn>, <jiang.xuexin@zte.com.cn>,
<zhang.yunkai@zte.com.cn>
Subject: Re: [PATCH] rps: process the skb directly if rps cpu not changed
Date: Tue, 21 Mar 2023 19:54:59 -0700 [thread overview]
Message-ID: <20230321195459.390dea45@kernel.org> (raw)
In-Reply-To: <202303212012296834902@zte.com.cn>
On Tue, 21 Mar 2023 20:12:29 +0800 (CST) yang.yang29@zte.com.cn wrote:
> The measured result shows the patch brings 50% reduction of NET_RX softirqs.
> The test was done on the QEMU environment with two-core CPU by iperf3.
> taskset 01 iperf3 -c 192.168.2.250 -t 3 -u -R;
> taskset 02 iperf3 -c 192.168.2.250 -t 3 -u -R;
>
> Previous RPS:
> CPU0 CPU1
this header looks misalinged
> NET_RX: 45 0 (before iperf3 testing)
> NET_RX: 1095 241 (after iperf3 testing)
>
> Patched RPS:
> CPU0 CPU1
> NET_RX: 28 4 (before iperf3 testing)
> NET_RX: 573 32 (after iperf3 testing)
This table is really confusing. What's the unit, how is it measured
and why are you showing before/after rather than the delta?
> diff --git a/net/core/dev.c b/net/core/dev.c
> index c7853192563d..c33ddac3c012 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -5666,8 +5666,9 @@ static int netif_receive_skb_internal(struct sk_buff *skb)
> if (static_branch_unlikely(&rps_needed)) {
> struct rps_dev_flow voidflow, *rflow = &voidflow;
> int cpu = get_rps_cpu(skb->dev, skb, &rflow);
> + int current_cpu = smp_processor_id();
>
> - if (cpu >= 0) {
> + if (cpu >= 0 && cpu != current_cpu) {
> ret = enqueue_to_backlog(skb, cpu, &rflow->last_qtail);
> rcu_read_unlock();
> return ret;
> @@ -5699,8 +5700,9 @@ void netif_receive_skb_list_internal(struct list_head *head)
> list_for_each_entry_safe(skb, next, head, list) {
> struct rps_dev_flow voidflow, *rflow = &voidflow;
> int cpu = get_rps_cpu(skb->dev, skb, &rflow);
> + int current_cpu = smp_processor_id();
This does not have to be in the loop.
>
> - if (cpu >= 0) {
> + if (cpu >= 0 && cpu != current_cpu) {
Please answer Yunsheng's question as well..
next prev parent reply other threads:[~2023-03-22 2:55 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-21 12:12 [PATCH] rps: process the skb directly if rps cpu not changed yang.yang29
2023-03-22 2:02 ` Yunsheng Lin
2023-03-22 7:21 ` [PATCH v5 2/6] ksm: support unsharing zero pages placed by KSM xu xin
2023-03-22 7:24 ` [PATCH] rps: process the skb directly if rps cpu not changed xu xin
2023-03-23 9:01 ` Yunsheng Lin
2023-03-23 10:04 ` xu xin
2023-03-23 10:47 ` Yunsheng Lin
2023-03-22 2:54 ` Jakub Kicinski [this message]
2023-03-22 3:03 ` Eric Dumazet
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