Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Jesper Dangaard Brouer <jbrouer@redhat.com>
Message-ID: <6396223c-6008-0e1b-e6ed-79c04c87a5e0@redhat.com>
Date:   Wed, 26 Jul 2023 11:22:40 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.10.0
Cc:     brouer@redhat.com, Dexuan Cui <decui@microsoft.com>,
        KY Srinivasan <kys@microsoft.com>,
        Paul Rosswurm <paulros@microsoft.com>,
        "olaf@aepfle.de" <olaf@aepfle.de>,
        "vkuznets@redhat.com" <vkuznets@redhat.com>,
        "davem@davemloft.net" <davem@davemloft.net>,
        "wei.liu@kernel.org" <wei.liu@kernel.org>,
        "edumazet@google.com" <edumazet@google.com>,
        "kuba@kernel.org" <kuba@kernel.org>,
        "pabeni@redhat.com" <pabeni@redhat.com>,
        "leon@kernel.org" <leon@kernel.org>,
        Long Li <longli@microsoft.com>,
        "ssengar@linux.microsoft.com" <ssengar@linux.microsoft.com>,
        "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
        "daniel@iogearbox.net" <daniel@iogearbox.net>,
        "john.fastabend@gmail.com" <john.fastabend@gmail.com>,
        "bpf@vger.kernel.org" <bpf@vger.kernel.org>,
        "ast@kernel.org" <ast@kernel.org>,
        Ajay Sharma <sharmaajay@microsoft.com>,
        "hawk@kernel.org" <hawk@kernel.org>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "shradhagupta@linux.microsoft.com" <shradhagupta@linux.microsoft.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Ilias Apalodimas <ilias.apalodimas@linaro.org>
Subject: Re: [PATCH V3,net-next] net: mana: Add page pool for RX buffers
Content-Language: en-US
To:     Haiyang Zhang <haiyangz@microsoft.com>,
        Jesper Dangaard Brouer <jbrouer@redhat.com>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>
References: <1689966321-17337-1-git-send-email-haiyangz@microsoft.com>
 <1af55bbb-7aff-e575-8dc1-8ba64b924580@redhat.com>
 <PH7PR21MB3116F8A97F3626AB04915B96CA02A@PH7PR21MB3116.namprd21.prod.outlook.com>
 <PH7PR21MB311675E57B81B49577ADE98FCA02A@PH7PR21MB3116.namprd21.prod.outlook.com>
 <729b360c-4d79-1025-f5be-384b17f132d3@redhat.com>
 <PH7PR21MB3116F5612AA8303512EEBA4CCA03A@PH7PR21MB3116.namprd21.prod.outlook.com>
In-Reply-To: <PH7PR21MB3116F5612AA8303512EEBA4CCA03A@PH7PR21MB3116.namprd21.prod.outlook.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk


On 25/07/2023 21.02, Haiyang Zhang wrote:
> 
>> -----Original Message-----
>> From: Jesper Dangaard Brouer <jbrouer@redhat.com>
>> Sent: Tuesday, July 25, 2023 2:01 PM
>>>>
>>>> Our driver is using NUMA 0 by default, so I implicitly assign NUMA node id
>>>> to zero during pool init.
>>>>
>>>> And, if the IRQ/CPU affinity is changed, the page_pool_nid_changed()
>>>> will update the nid for the pool. Does this sound good?
>>>>
>>>
>>> Also, since our driver is getting the default node from here:
>>> 	gc->numa_node = dev_to_node(&pdev->dev);
>>> I will update this patch to set the default node as above, instead of implicitly
>>> assigning it to 0.
>>>
>>
>> In that case, I agree that it make sense to use dev_to_node(&pdev->dev),
>> like:
>> 	pprm.nid = dev_to_node(&pdev->dev);
>>
>> Driver must have a reason for assigning gc->numa_node for this hardware,
>> which is okay. That is why page_pool API allows driver to control this.
>>
>> But then I don't think you should call page_pool_nid_changed() like
>>
>> 	page_pool_nid_changed(rxq->page_pool, numa_mem_id());
>>
>> Because then you will (at first packet processing event) revert the
>> dev_to_node() setting to use numa_mem_id() of processing/running CPU.
>> (In effect this will be the same as setting NUMA_NO_NODE).
>>
>> I know, mlx5 do call page_pool_nid_changed(), but they showed benchmark
>> numbers that this was preferred action, even-when sysadm had
>> "misconfigured" the default smp_affinity RX-processing to happen on a
>> remote NUMA node.  AFAIK mlx5 keeps the descriptor rings on the
>> originally configured NUMA node that corresponds to the NIC PCIe slot.
> 
> In mana_gd_setup_irqs(), we set the default IRQ/CPU affinity to gc->numa_node
> too, so it won't revert the nid initial setting.
> 
> Currently, the Azure hypervisor always indicates numa 0 as default. (In
> the future, it will start to provide the accurate default dev node.) When a
> user manually changes the IRQ/CPU affinity for perf tuning, we want to
> allow page_pool_nid_changed() to update the pool. Is this OK?
> 

If I were you, I would wait with the page_pool_nid_changed()
"optimization" and do a benchmark mark to see if this actually have a
benefit.  (You can do this in another patch).  (In a Azure hypervisor
environment is might not be the right choice).

This reminds me, do you have any benchmark data on the improvement this
patch (using page_pool) gave?

--Jesper