netdev - Re: Regression: kernel 4.14 an later very slow with many ipsec tunnels

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Message-Id: <20180913.141239.123063658850697631.davem@davemloft.net>
Date:   Thu, 13 Sep 2018 14:12:39 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     fw@...len.de
Cc:     linux@...m.de, netdev@...r.kernel.org,
        steffen.klassert@...unet.com, linux-kernel@...r.kernel.org,
        torvalds@...ux-foundation.org, christophe.gouault@...nd.com
Subject: Re: Regression: kernel 4.14 an later very slow with many ipsec
 tunnels

From: Florian Westphal <fw@...len.de>
Date: Thu, 13 Sep 2018 23:03:25 +0200

> I am staring at b58555f1767c9f4e330fcf168e4e753d2d9196e0
> but can't figure out how to configure that away from the
> 'no hashing for prefixed policies' default or why we even have
> policy_inexact in first place :/
> 
> I'll look at this again tomorrow.

The inexact list exists to handle prefixed input keys.

At the time that I wrote all of the control plane hash table
stuff, configurations I could find consisted of:

1) Entires with non-prefixed keys, which are easy to hash.
   The number of entries could be large (e.g. cell phone
   network)

2) A very small number of prefixed policies.

So hashing, when possible, falling back to the linked list
for prefixed stuff.

Beforehand we only had the linked list :-)