On 2020-12-17 17:09, Jamal Hadi Salim wrote:
On 2020-12-16 6:47 a.m., Maxim Mikityanskiy wrote:
On 2020-12-15 18:37, Jamal Hadi Salim wrote:
[..]
Same question above:
Is there a limit to the number of classes that can be created?
Yes, the commit message of the mlx5 patch lists the limitations of our
NICs. Basically, it's 256 leaf classes and 3 levels of hierarchy.
Ok, thats what i was looking for.
IOW, if someone just created an arbitrary number of queues do they
get errored-out if it doesnt make sense for the hardware?
The current implementation starts failing gracefully if the limits are
exceeded. The tc command won't succeed, and everything will roll back
to the stable state, which was just before the tc command.
Does the user gets notified somehow or it fails silently?
An extack message would help.
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1;
t=1608288498; bh=RMhOdIb4utXHB89dvxKO9kM+jQNSV+kIKsJ0O6KNJWs=;
h=Subject:To:CC:References:From:Message-ID:Date:User-Agent:
MIME-Version:In-Reply-To:Content-Type:Content-Language:
Content-Transfer-Encoding:X-Originating-IP:X-ClientProxiedBy;
b=pThe8Bqxykn4jFcf5ZYZMSgEPZZBiId+lReLZZ9KFCdbROoDwWPTGDWFNhOADAvRA
7bjihDOFAvu2+MXP1m9/IS0lQgKXa2iOKAk5S1QwZj+aF5m9bZ1ya7uRSZiK7k32Tp
cPyfic9k+SXTN0zyJovtWc5i4QlwnHWCQ7zPvMYwB4Kmvmk/YiRwIQvEooMDQaq92Z
7+scnlRaNVAEd8ZERye9Fxa7htaGiUArPQR3aS7ol1QmrCXaN1hZA84lySCaLcJ6JA
6qFKvjj0XWP0TsYJqpZzkS+F0yfGOAphtaIMWq/o8m5Julk0e90Yj6maRvGG3kFOaY
c4zEilz1uAHKA==
The current implementation doesn't use extack, just returns an error
code, because many callbacks to the qdisc don't get extack as a
parameter. However, I agree with you, these messages would be helpful
for the user when an operation fails due to hardware limitations - it
will be easier than guessing what caused a EINVAL, so I'll add them. I
will review which callbacks lacked an extack, and I might add it if it's
meaningful for them.
If such limits exist, it may make sense to provide a knob to query
(maybe ethtool)
Sounds legit, but I'm not sure what would be the best interface for
that. Ethtool is not involved at all in this implementation, and AFAIK
it doesn't contain any existing command for similar stuff. We could
hook into set-channels and add new type of channels for HTB, but the
semantics isn't very clear, because HTB queues != HTB leaf classes,
and I don't know if it's allowed to extend this interface (if so, I
have more thoughts of extending it for other purposes).
More looking to make sure no suprise to the user. Either the user can
discover what the constraints are or when they provision they get a
a message like "cannot offload more than 3 hierarchies" or "use devlink
if you want to use more than 256 classes", etc.
Yes, it makes perfect sense. Messages are even more user-friendly, as
for me. So, I'll add such messages to extack, and as the limitations are
driver-specific, I'll pass extack to the driver.
I will respin when net-next reopens, in the meanwhile comments are welcome.
Thanks,
Max
cheers,
jamal
