linux-kernel - Re: [PATCH 00/13] lib/generic-radix-tree: genradix bug fix and optimisations.

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Message-ID: <20200825163224.GA499490@zaphod.evilpiepirate.org>
Date:   Tue, 25 Aug 2020 12:32:24 -0400
From:   Kent Overstreet <kent.overstreet@...il.com>
To:     David Laight <David.Laight@...lab.com>
Cc:     'Marcelo Ricardo Leitner' <marcelo.leitner@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "'linux-sctp@...r.kernel.org'" <linux-sctp@...r.kernel.org>,
        Eric Biggers <ebiggers@...nel.org>,
        'Catalin Marinas' <catalin.marinas@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        'Neil Horman' <nhorman@...driver.com>
Subject: Re: [PATCH 00/13] lib/generic-radix-tree: genradix bug fix and
 optimisations.

On Tue, Aug 25, 2020 at 04:00:35PM +0000, David Laight wrote:
> From: 'Marcelo Ricardo Leitner'
> > Sent: 25 August 2020 16:41
> > 
> > On Tue, Aug 25, 2020 at 02:52:34PM +0000, David Laight wrote:
> > > The genradix code is used by SCTP for accessing per-stream data.
> > > This means there are quite a lot of lookups but the code wasn't
> > > really optimised at all.
> > 
> > My test box is down for the moment and will bring it on later today or
> > tomorrow, so I can't test it yet. What should we expect as performance
> > gains here?
> 
> Not sure, probably not much, but it ought to show up :-)
> There'll be bigger gains on a cpu that has software ilog2().
> 
> I've only checked SCTP still works.
> I've requested 32k streams on a listener - to force a level-2 tree.
> I've also done at least one check with a massive pad in the sctp
> stream structure.

Have you benchmarked at all? Or were you looking at the generated assembly?