netdev - Re: [PATCH net-next 0/9] net: Kernel side filtering for route dumps

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Message-Id: <20181011.122847.1015772734131510783.davem@davemloft.net>
Date:   Thu, 11 Oct 2018 12:28:47 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     dsahern@...il.com
Cc:     jhs@...atatu.com, sowmini.varadhan@...cle.com,
        stephen@...workplumber.org, dsahern@...nel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH net-next 0/9] net: Kernel side filtering for route dumps

From: David Ahern <dsahern@...il.com>
Date: Thu, 11 Oct 2018 12:44:49 -0600

> I disagree with your overall premise of bpf the end-all hammer. It is a
> tool but not the only tool. For starters, you are proposing building the
> message, run the filter on it, and potentially back the message up to
> drop the recently added piece because the filter does not want it
> included. That is still wasting a lot of cpu cycles to build and drop. I
> am thinking about scale to 1 million routes -- I do not need the dump
> loop building a message for 1 million entries only to drop 99% of them.
> That is crazy.

I completely agree.

Once you've composed the message, the whole point of filtering is lost.