linux-kernel - Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to refcount

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Date:   Mon, 20 Mar 2017 11:39:37 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     David Miller <davem@...emloft.net>
Cc:     herbert@...dor.apana.org.au, eric.dumazet@...il.com,
        elena.reshetova@...el.com, keescook@...omium.org,
        netdev@...r.kernel.org, bridge@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, kuznet@....inr.ac.ru,
        jmorris@...ei.org, kaber@...sh.net, stephen@...workplumber.org,
        ishkamiel@...il.com, dwindsor@...il.com, akpm@...ux-foundation.org
Subject: Re: [PATCH 07/17] net: convert sock.sk_refcnt from atomic_t to
 refcount_t

On Sat, Mar 18, 2017 at 06:21:21PM -0700, David Miller wrote:
> From: Herbert Xu <herbert@...dor.apana.org.au>
> Date: Sun, 19 Mar 2017 00:47:59 +0800
> 
> > Eric Dumazet <eric.dumazet@...il.com> wrote:
> >> On Fri, 2017-03-17 at 07:42 +0000, Reshetova, Elena wrote:
> >> 
> >>> Should we then first measure the actual numbers to understand what we
> >>> are talking here about? 
> >>> I would be glad to do it if you suggest what is the correct way to do
> >>> measurements here to actually reflect the real life use cases. 
> >> 
> >> How have these patches been tested in real life exactly ?
> >> 
> >> Can you quantify number of added cycles per TCP packet, where I expect
> >> we have maybe 20 atomic operations in all layers ...
> > 
> > I completely agree.  I think this thing needs to default to the
> > existing atomic_t behaviour.
> 
> I totally agree as well, the refcount_t facility as-is is unacceptable
> for networking.

Can we at least give a benchmark and have someone run numbers? We should
be able to quantify these things.