netdev - Re: [PATCH net-next 1/4] netlink: truncate overlength attribute list in nla_nest

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Message-ID: <20230607095254.20a3394c@hermes.local>
Date: Wed, 7 Jun 2023 09:52:54 -0700
From: Stephen Hemminger <stephen@...workplumber.org>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Gal Pressman <gal@...dia.com>, Edwin Peer <espeer@...il.com>, David
 Ahern <dsahern@...il.com>, netdev <netdev@...r.kernel.org>, Andrew
 Gospodarek <andrew.gospodarek@...adcom.com>, Michael Chan
 <michael.chan@...adcom.com>, Michal Kubecek <mkubecek@...e.cz>
Subject: Re: [PATCH net-next 1/4] netlink: truncate overlength attribute
 list in nla_nest_end()

On Wed, 7 Jun 2023 09:33:24 -0700
Jakub Kicinski <kuba@...nel.org> wrote:

> > > 
> > > The problem is basically that attributes can only be 64kB and 
> > > the legacy SR-IOV API wraps all the link info in an attribute.    
> > 
> > Isn't that a second order issue? The skb itself is limited to 32kB AFAICT.  
> 
> Hm, you're right. But allocation larger than 32kB are costly.
> We can't make every link dump allocate 64kB, it will cause
> regressions on systems under memory pressure (== real world).
> 
> You'd need to come up with some careful scheme of using larger
> buffers.

Why does it all have to be a single message?
Things like 3 million routes are dumped fine, as multiple messages.