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Date:   Fri, 14 Dec 2018 17:23:33 +0100
From:   Florian Westphal <fw@strlen.de>
To:     Christophe Gouault <christophe.gouault@6wind.com>
Cc:     Florian Westphal <fw@strlen.de>, Wolfgang Walter <linux@stwm.de>,
        David Miller <davem@davemloft.net>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        Steffen Klassert <steffen.klassert@secunet.com>
Subject: Re: INFO: rcu detected stall in xfrm_hash_rebuild
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Christophe Gouault <christophe.gouault@6wind.com> wrote:
> The main use cases I have encountered and tried to address with the
> hash-based lookup were network operator use cases:
> - a lot of dynamic /32 <=> /32 policies (protecting GTP tunnels)
> - or a lot of dynamic policies with the same prefix lengths (e.g. /16 <=> /24)
> and a few non-hashed policies stored in the linked list.

Thanks for the detailed information.

[..]

> Could you verify how the configuration time would behave in such use
> cases if the hash-based lookup was replaced by a tree-based lookup?

I won't send a patch to remove your work, at least not at this time.

In case I'd do this removal (thresholds, hash table, or both)
i will make these tests to see how large the impact is.