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

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Message-Id: <20170318.182121.439615057765380575.davem@davemloft.net>
Date:   Sat, 18 Mar 2017 18:21:21 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     herbert@...dor.apana.org.au
Cc:     eric.dumazet@...il.com, elena.reshetova@...el.com,
        keescook@...omium.org, peterz@...radead.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

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.