And to answer my last question about SMP capabilities, it looks like the
only locking going on is when the driver is talking to the Kernel itself
through kstat which would make sense. So yes it looks like mcx does have
SMP support :) Well its enough for me to buy a card from ebay to play with
as the ConnectX-4 Lx cards are pretty cheap now.
Warning to others reading my comments, me poking around in kernel code is
akin to a blind person in a library before learning braille, so take
nothing I say as fact, merely optimistic opinion :)
On Wed, Sep 29, 2021 at 9:08 PM Andrew Lemin <andrew.lemin@gmail.com> wrote:
> So I think I have figured out some things Theo browsing through
> https://github.com/openbsd/src/blob/master/sys/dev/pci/if_mcx.c.
>
> I can see that some offloading is supported, but have not yet figured out
> how much is implemented yet. It looks like the offloading capability in
> these cards are much more granular than I have understood from previous
> hardware.
> I was able to decipher some of it using this
> https://www.mellanox.com/related-docs/user_manuals/Ethernet_Adapters_Programming_Manual.pdf
> (this is very well written).
>
> And I was quite excited to see what looks like the RDMA access support in
> the mcx driver! So we should be able to see the super low latency
> capabilities with this card :)
>
> I will keep pushing myself.. Thanks again Theo
>
> On Wed, Sep 29, 2021 at 2:21 PM Andrew Lemin <andrew.lemin@gmail.com>
> wrote:
>
>> Hi Theo :)
>>
>> Ok sure, I will put on my cape-of-courage and start reading the source..
>> I may be some time!
>>
>> On Wed, Sep 29, 2021 at 1:56 PM Theo de Raadt <deraadt@openbsd.org>
>> wrote:
>>
>>> We tend to keep our driver manual pages without detailed promises.
>>> They do ethernet, they do it best effort, etc.
>>>
>>> What you want to know can be found by reading the source, or the
>>> commit logs. Since this is a locally written driver, the code is
>>> surprisingly approachable.
>>>
>>> Andrew Lemin <andrew.lemin@gmail.com> wrote:
>>>
>>> > Hi. I hope everyone is well and having a great day :)
>>> >
>>> > Just a quick question about the mcx (Mellanox 5th generation Ethernet
>>> > device) drivers
>>> > https://man.openbsd.org/mcx.4
>>> >
>>> > The man page says nothing more than it supports;
>>> > ConnectX-4 Lx EN
>>> > ConnectX-4 EN
>>> > ConnectX-5 EN
>>> > ConnectX-6 EN
>>> >
>>> > I am looking for some clarity on what features and performance
>>> > characteristics mcx boasts?
>>> >
>>> > For example are the following basic hardware features supported by this
>>> > driver?
>>> > IPv4 receive IP/TCP/UDP checksum offload
>>> > IPv4 transmit TCP/UDP checksum offload
>>> > VLAN tag insertion and stripping
>>> > interrupt coalescing
>>> >
>>> > And what other features does it support?
>>> >
>>> > I also came across a comment in some forum a while back (so high
>>> quality
>>> > information 😉) that mentioned Mellanox drivers in OpenBSD are SMP
>>> safe and
>>> > so not giant-locked. Is this true?
>>> >
>>> > Thanks, Andy,
>>>
>>
No comments:
Post a Comment