linux-kernel - RE: [PATCH V2 net-next] net: mana: Assigning IRQ affinity on HT cores

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Date:   Tue, 21 Nov 2023 17:37:11 +0000
From:   Haiyang Zhang <haiyangz@...rosoft.com>
To:     Souradeep Chakrabarti <schakrabarti@...ux.microsoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        Long Li <longli@...rosoft.com>,
        "sharmaajay@...rosoft.com" <sharmaajay@...rosoft.com>,
        "leon@...nel.org" <leon@...nel.org>,
        "cai.huoqing@...ux.dev" <cai.huoqing@...ux.dev>,
        "ssengar@...ux.microsoft.com" <ssengar@...ux.microsoft.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>
CC:     Souradeep Chakrabarti <schakrabarti@...rosoft.com>,
        Paul Rosswurm <paulros@...rosoft.com>
Subject: RE: [PATCH V2 net-next] net: mana: Assigning IRQ affinity on HT cores



> -----Original Message-----
> From: Souradeep Chakrabarti <schakrabarti@...ux.microsoft.com>
> Sent: Tuesday, November 21, 2023 8:55 AM


> +	/* for each interrupt find the cpu of a particular
> +	 * sibling set and if it belongs to the specific numa
> +	 * then assign irq to it and clear the cpu bit from
> +	 * the corresponding avail_cpus.
> +	 * Increase the cpu_count for that node.
> +	 * Once all cpus for a numa node is assigned, then
> +	 * move to different numa node and continue the same.
> +	 */
> +	for (i = irq_start; i < nvec; ) {
> +
> +		/* check if the numa node has cpu or not
> +		 * to avoid infinite loop.
> +		 */
> +		if (cpumask_empty(cpumask_of_node(numa_node))) {
> +			numa_node++;

Since it starts at start_numa_node, we should consider roll over at the 
num_online_nodes() like the code below:
				if (numa_node == num_online_nodes())
					numa_node = 0;

It should also check empty for the next one.
And set node_count = 0; after the loop.

> +			if (++node_count == num_online_nodes()) {
> +				err = -EAGAIN;
Consider return -ENODEV, because we are not asking for retry.

> +				goto free_irq;
> +			}
> +		}

Thanks,
- Haiyang