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

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Message-ID: <20230607102944.09bb1216@kernel.org>
Date: Wed, 7 Jun 2023 10:29:44 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Stephen Hemminger <stephen@...workplumber.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 09:52:54 -0700 Stephen Hemminger wrote:
> > 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.

The old API we can't change. The new API is switchdev / devlink,
and it's already in place. We'd have to add a third API, like 
the old one but with different msg format which for obvious 
reasons I'd prefer not to do.