Re: Network Stack Budgeting

["Tomas Pilar (tpilar)" <tpilar@solarflare.com>]

Hi Siyuan,

I had to do some tweaks due to the fact that people in the wild want to PXE boot whole WDS installations which are upwards of 300MB.

I have an internal set of queues where the NIC receives into. Snp.Receive() will get a packet from this store. I had to implement a separate queue for unicast/multicast/broadcast traffic so that I could reprioritise and deliver unicast traffic while under ARP spam. I tied internal poll to receive and transmit, so Snp.Receive() will poll the NIC and then dequeue a packet while Snp.Transmit() will transmit the packet and then poll the NIC to get a completion. I also implemented a busy poll for 100us or until the next packet comes in when the NIC is polled.

Otherwise I have seen a pathological case where the TFTP client would pull one packet per second but the TFTP_RETRANSMIT interval on the server was also one second and everything was awful.

In theory the busy poll moderator might cause an issue in a pathological case, if it stalls the machine for 100us for each packet - with 100 packets per second this would eat only 10ms.

Cheers,
Tom

On 27/01/2019 14:28, Fu, Siyuan wrote:
> Hi, Tom
>
>> -----Original Message-----
>> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Tomas
>> Pilar (tpilar)
>> Sent: Friday, January 25, 2019 8:09 PM
>> To: Wu, Jiaxin <jiaxin.wu@intel.com>; Laszlo Ersek <lersek@redhat.com>; edk2-
>> devel@lists.01.org
>> Cc: Ye, Ting <ting.ye@intel.com>
>> Subject: Re: [edk2] Network Stack Budgeting
>>
>> Yeah, that makes sense I suppose. The end result is however that the network
>> device is 'opened' as soon as ConnectController() is called rather than when
>> someone wants to do networking. This seems wrong and directly leads to a DoS
>> of a platform in case of heavy network load (unless we implement budgeting in
>> the network driver, which is a really not what it should be doing).
> It's true that a configured MNP will start a background system poll to receive
> network packets, but normally it won't lead to a DoS, because the receive frequency 
> is actually very low. The MNP driver only tries to receive 1 packet from SNP for every
> 10 milliseconds (see MNP_SYS_POLL_INTERVAL, MnpSystemPoll() and related timer event).
> So no matter how heavy the network is, MNP driver (and upper layer stack) will
> only process at most 100 packets per second, all other packets should be dropped
> by UNDI driver directly.
>
> So if there is nobody doing busy network receiving, the network stack cost will be
> at most 100 packets per NIC device and per second.
>
> In your first email you mentioned "some performance improvements to my network driver",
> may I know what's the improvement method you are using?
>
> Best Regards,
> Siyuan
>
>> How do you suggest we solve this problem?
>>
>> Cheers,
>> Tom
>>
>> On 25/01/2019 08:44, Wu, Jiaxin wrote:
>>> Hi Tom,
>>>
>>> One thing I want to highlight is that our design of network stack is not
>> only for the PXE/HTTP boot trigged in BootManager, but also to make sure it's
>> workable once there is any MNP instance configured by upper drivers
>> (ARP/IPv4/IPv6).
>>> Take ARP/IP as an example, once ARP/IP are started, we need a heartbeat to
>> process any ARP requests, which is required by ARP functionality. In such a
>> case, SNP must be started to make ARP/IP drivers works well.
>>> Thanks,
>>> Jiaxin
>>>
>>>> -----Original Message-----
>>>> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
>>>> Tomas Pilar (tpilar)
>>>> Sent: Friday, January 25, 2019 1:43 AM
>>>> To: Laszlo Ersek <lersek@redhat.com>; edk2-devel@lists.01.org
>>>> Subject: Re: [edk2] Network Stack Budgeting
>>>>
>>>>
>>>>
>>>> On 24/01/2019 16:49, Laszlo Ersek wrote:
>>>>> On 01/24/19 14:25, Tomas Pilar (tpilar) wrote:
>>>>>> Hmm,
>>>>>>
>>>>>> Mnp->Configure() will eventually call MnpStartSnp().
>>>>>>
>>>>>> A grep for Mnp->Configure shows that:
>>>>>> * ArpDxe performs this on DriverBinding.Start()
>>>>>> * Ip6Dxe performs this on DriverBinding.Start()
>>>>>>
>>>>>> Ipv4 and DnsDhcp do this as a part of their Configure() they expose in
>> the
>>>> API.
>>>>> Yes, that makes sense. All of the above drivers are UEFI drivers that
>>>>> follow the UEFI driver model, AIUI. As long as the controller is not
>>>>> connected from BDS, no BindingStart() function should be called in these.
>>>> Ah, but I would expect the BDS to call ConnectController() on the NIC, but
>> I
>>>> would not expect the network stack to be started unless the device is
>>>> actually chosen for PXE booting. In other words, the above protocols should
>>>> follow the example of EFI_DNS4_PROTOCOL that binds against the device
>>>> during BDS but .Configure() is not automatically called by
>>>> DriverBinding.Start().
>>>>
>>>> .Configure() should be called by the BootManager if networking is actually
>> to
>>>> be done. That in turn will configure Mnp and start Snp.
>>>>
>>>> Cheers,
>>>> Tom
>>>>
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