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

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Date:   Tue, 02 Oct 2018 16:45:56 +0200
From:   Wolfgang Walter <linux@...m.de>
To:     Florian Westphal <fw@...len.de>
Cc:     Steffen Klassert <steffen.klassert@...unet.com>,
        David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        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

Hello,

Am Freitag, 14. September 2018, 07:54:37 schrieb Florian Westphal:
> Steffen Klassert <steffen.klassert@...unet.com> wrote:
> > On Thu, Sep 13, 2018 at 11:03:25PM +0200, Florian Westphal wrote:
> > > David Miller <davem@...emloft.net> wrote:
> > > > From: Florian Westphal <fw@...len.de>
> > > > Date: Thu, 13 Sep 2018 18:38:48 +0200
> > > > 
> > > > > Wolfgang Walter <linux@...m.de> wrote:
> > > > >> What I can say is that it depends mainly on number of policy rules
> > > > >> and SA.
> > > > > 
> > > > > Thats already a good hint, I guess we're hitting long hash chains in
> > > > > xfrm_policy_lookup_bytype().
> > > > 
> > > > I don't really see how recent changes can influence that.
> > > 
> > > I don't think there is a recent change that did this.
> > > 
> > > Walter says < 4.14 is ok, so this is likely related to flow cache
> > > removal.
> > > 
> > > F.e. it looks like all prefixed policies end up in a linked list
> > > (net->xfrm.policy_inexact) and are not even in a hash table.
> > > 
> > > 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 :/
> > 
> > The hash threshold can be configured like this:
> > 
> > ip x p set hthresh4 0 0
> > 
> > This sets the hash threshold to local /0 and remote /0 netmasks.
> > With this configuration, all policies should go to the hashtable.
> 
> Yes, but won't they all be hashed to same bucket?
> 
> [ jhash(addr & 0, addr & 0) ] ?
> 
> > Default hash thresholds are local /32 and remote /32 netmasks, so
> > all prefixed policies go to the inexact list.
> 
> Yes.
> 
> Wolfgang, before having to work on getting perf into your router image
> can you perhaps share a bit of info about the policies you're using?
> 
> How many are there?  Are they prefixed or not ("10.1.2.1")?

Since my last reply to this message I didn't get a reply: is there any 
progress how to fix this performance regression I missed?

Or are we stuck here with longterm kernel 4.9 for a long time?


Regards,
-- 
Wolfgang Walter
Studentenwerk München
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